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COPYRIGHT DEPOSIT 



THE STORY OF 
A PIECE OF COAL 

WHAT IT IS, WHENCE IT COMES, 
AND WHITHER IT GOES 



BY 

EDWARD Ar\MARTIN, F.G.S. 

AUTHOR OF AMIDST NATURE'S REALMS, ETC. 




WITH THIRTY-EIGHT ILLUSTRATIONS 



NEW YORK 
MCMXV 



I 






.i^U 



Copyright, 1896, 1915 
By t). APPLETON AND COMPANY 



Printed in the United States of America 



M2DIB16 

,, -1 ,n ©GLA4185J49 

?/7 j , 




Fig. i. — A Forest of the Coal period. 



PREFACE. 



When the first edition of this book was pub- 
lished, Great Britain was the leading coal-pro- 
duction country of the world. In 1899, the United 
States supplanted Great Britain in the position 
of leadership, and since then the relative im- 
portance of this country has steadily advanced. 
In the 14 years from 1899 to 1913, the coal pro- 
duction of the United States increased from 254 
million tons to 570 million tons, a gain of nearly 
125 per cent. The production in Great Britain 
in the same period has increased a little over 30 
per cent., from 247 million tons to 322 million 
tons. Germany, which ranks third among the 
coal-producing countries, has increased her pro- 
duction by 88 per cent., a ratio nearly three times 
that of Great Britain, from 150 million tons in 
1899 to 282 million tons in 1913. The combined 
production of Great Britain and Germany ex- 
ceeds that of the United States by less than 6 per 
cent. The total production of the world in 1913 
was approximately 1,444 million tons, of which 
the United States contributed nearly 40 per cent. 

5 



6 PREFACE. 

The development of the coal-mining indus- 
try in the United States to its present vast pro- 
portions, considered with the increase in the pop- 
ulation, presents some interesting comparisons. 
The use of mineral fuel became an important 
factor in the manufacture of iron about the mid- 
dle of the last century. In 1850, the production 
of coal amounted to 7,018,000 tons, or at the 
rate of three-tenths of a ton for each of the 
23,192,000 inhabitants. In i860, the production 
was still less than one-half ton per person, but 
in 1880, when the population had increased to 
50,189,000, the production of coal was 71,482,- 
000 tons, an average of 1.42 tons per capita. In 
1900, the production averaged 3.53 tons for each 
inhabitant, and in 1913 the average production 
rose to 5.87 tons. 

A material of such immense importance to 
the industrial and commercial prosperity of the 
country is its own recommendation to careful 
study. The story of coal as told in the follow- 
ing pages gives the main facts of its origin, oc- 
currence, distribution, mining, and application, 
in a form which has proved attractive to many 
thousands of readers. 

July, 1915. 



CONTENTS. 



CHAPTER 

I. The Origin of Coal and the Plants of 

WHICH IT IS COMPOSED . 

II. A General- View of the Coal-bearing 
Strata . 

III. Various Forms of Coal and Carbon . 

IV. The Coal-mine and its Dangers . 
V. Early History — its Use and its Abuse 

VI. How Gas is made — Illuminating Oils and 

Bye-products . . . 
VII. The Coal Supplies of the World 
VIII. The Coal-tar Colours . 

Chart showing Products of Coal 
Index 



36 

64 

84 

101 

in 
140 
155 
165 
166 



LIST OF ILLUSTRATIONS. 



FIGURE 

1. A Forest of the Coal period 

2. Annularia radiata . 

3. Rhacopteris incequilatera 

4. Frond of Pecopteris . 

5. Pecopteris Serlii 

6. Sphenopteris affinis . 

7. Calamites Suckowii . 

8. Calamocladus grandis 

9. Asterophyllites foliosa 

10. Sphenophyllum cuneifolium 

11. Cast of Lepidodendron 

12. Lepidodendron longifolium 

13. Lepidodendron aculeatum 

14. Lepidostrobus 

15. Lycopodites 

16. Stigmaria ficoides 

17. Section of Stigmaria 

18. Sigillarian Trunks in Sandstone 

19. Productus . 

20. Encrinite . 

21. Encrinital Limestone 

22. Various encrinites 

23. Cyathophyllum . 

24. Archegosaurus minor 

25. Psammodus porosus 

26. Orthoceras. 
2J. Fene stella retipora 

28. Goniatites . 

29. -^ viculopecten papyraceus 

30. Fragment of Lepidodendron 

31. Engine-house at Head of a Coal-pit 

32. Gas Jet and Davy Lamp . 

33. Part of a Sigillarian Trunk 

34. Inside a Gas-holder . 

35. Filling Retorts by Machinery 

36. " Condensers " . 

37. " Washers "... 

38. " Purifiers" 

3 



Frontispiece 



13 

14 
15 
16 

17 
19 
20 
21 
23 
24 
25 
25 
26 
27 
30 
32 
41 
42 

45 
46 

47 

55 

61 

61 

62 

62 

63 

63 

77 

85 

92 

98 

114 

118 

119 

120 

121 



THE STORY OF A PIECE OF COAL. 



CHAPTER I. 

THE ORIGIN OF COAL AND THE PLANTS OF 
WHICH IT IS COMPOSED. 

From the homely scuttle of coal at the side of 
the hearth to the gorgeously verdant vegetation 
of a forest of mammoth trees, might have ap- 
peared a somewhat far cry in the eyes of those 
who lived some fifty years ago. But there are 
few now who do not know what was the origin of 
the coal which they use so freely, and which in 
obedience to their demand has been brought up 
more than a thousand feet from the bowels of the 
earth ; and, although familiarity has in a sense 
bred contempt for that which a few shillings will 
always purchase, in all probability a stray thought 
does occasionally cross one's mind, giving birth 
to feelings of a more or less thankful nature that 
such a store of heat and light was long ago laid 
up in this earth of ours for our use, when as yet 
man was not destined to put in an appearance for 
many, many ages to come. We can scarcely im- 
agine the industrial condition of England in the 
absence of so fortunate a supply of coal ; and the 
many good things which are obtained from it, and 
the uses to which, as we shall see, it can be put, 
do indeed demand recognition. 



IO THE STORY OF A PIECE OF COAL. 

Were our present forests uprooted and over- 
thrown, to be covered by sedimentary deposits 
such as those which cover our coal-seams, the 
amount of coal which would be thereby formed 
for use in some future age, would amount to a 
thickness of perhaps two or three inches at most, 
and yet, in one coal-field alone, that of West- 
phalia, the 117 most important seams, if placed 
one above the other in immediate succession, 
would amount to no less than 294 feet of coal. 
From this it is possible to form a faint idea of the 
enormous growths of vegetation required to form 
some of our representative coal-beds. But the 
coal is not found in one continuous bed. These 
numerous seams of coal are interspersed between 
many thousands of feet of sedimentary deposits, 
the whole of which form the " coal-measures." 
Now, each of these seams represents the growth 
of a forest, and to explain the whole series it is 
necessary to suppose that between each deposit 
the land became overwhelmed by the waters of 
the sea or lake, and after a long sub-aqueous 
period, was again raised into dry land, ready to 
become the birth-place of another forest, which 
would again beget, under similarly repeated con- 
ditions, another seam of coal. Of the conditions 
necessary to bring these changes about we will 
speak later on, but this instance is sufficient to 
show how inadequate the quantity of fuel would 
be, were we dependent entirely on our own exist- 
ing forest growths. 

However, we will leave for the present the 
fascinating pursuit of theorising as to the how 
and wherefore of these vast beds of coal, rele- 
gating the geological part of the study of the car- 
boniferous system to a future chapter, where will 



THE ORIGIN AND COMPOSITION OF COAL. II 

be found some more detailed account of the posi- 
tion of the coal-seams in the strata which contain 
them. At present the actual details of the coal 
itself will demand our attention. 

Coal is the mineral which has resulted, after 
the lapse of thousands of thousands of years, 
from the accumulations of vegetable material, 
caused by the steady yearly shedding of leaves, 
fronds and spores, from forests which existed in 
an early age ; these accumulated where the trees 
grew that bore them, and formed in the first 
place, perhaps, beds of peat ; the beds have since 
been subjected to an ever-increasing pressure of 
accumulating strata above them, compressing the 
sheddings of a whole forest into a thickness in 
some cases of a few inches of coal, and have been 
acted upon by the internal heat of the earth, 
which has caused them to part, to a varying de- 
gree, with some of their component gases. If we 
reason from analogy, we are compelled to admit 
that the origin of coal is due to the accumula- 
tion of vegetation, of which more scattered, but 
more distinct, representative specimens occur in 
the shales and clays above and below the coal- 
seams. But we are also able to examine the 
texture itself of the various coals by submitting 
extremely thin slices to a strong light under 
the microscope, and are thus enabled to decide 
whether the particular coal we are examining 
is formed of conifers, horse-tails, club-mosses, or 
ferns, or whether it consists simply of the accu- 
mulated sheddings of all, or perhaps, as in some 
instances, of innumerable spores. 

In this way the structure of coal can be accu- 
rately determined. Were we artificially to pre- 
pare a mass of vegetable substance, and covering 



12 THE STORY OF A PIECE OF COAL. 

it up entirely, subject it to great pressure, so that 
but little of the volatile gases which would be 
formed could escape, we might in the course of 
time produce something approaching coal, but 
whether we obtained lignite, jet, common bitumi- 
nous coal, or anthracite, would depend upon the 
possibilities of escape for the gases contained in 
the mass. 

Everybody has doubtless noticed that, when a 
stagnant pool which contains a good deal of de- 
caying vegetation is stirred, bubbles of gas rise 
to the surface from the mud below. This gas is 
known as marsh-gas, or light carburetted hydro- 
gen, and gives rise to the ignis fatuus which hovers 
about marshy land, and which is said to lure the 
weary traveller to his doom. The vegetable mud 
is here undergoing rapid decomposition, as there 
is nothing to stay its progress, and no superposed 
load of strata confining its resulting products 
within itself. The gases therefore escape, and 
the breaking-up of the tissues of the vegetation 
goes on rapidly. 

The chemical changes which have taken place 
in the beds of vegetation of the carboniferous 
epoch, and which have transformed it into coal, 
are even now but imperfectly understood. All 
we know is that, under certain circumstances, one 
kind of coal is formed, whilst under other condi- 
tions, other kinds have resulted ; whilst in some 
cases the processes have resulted in the prepara- 
tion of large quantities of mineral oils, such as 
naphtha and petroleum. Oils are also artificially 
produced from the so-called waste-products of the 
gas-works, but in some parts of the world the 
process of their manufacture has gone on natu- 
rally, and a yearly increasing quantity is being util- 



THE ORIGIN AND COMPOSITION OF COAL. 13 



ised. In England oil has been pumped up from 
the carboniferous strata of Coalbrook Dale, whilst 
in Sussex it has been found in smaller quantities, 
where, in all probability, it has had its origin in 
the lignitic beds of the Wealden strata. Immense 
quantities are used for fuel by the Russian steamers 
on the Caspian Sea, the Baku petroleum wells be- 
ing a most valuable possession. In Sicily, Persia, 
and, far more important, in the United States, 
mineral oils are 
found in great 
quantity. 

In all probabil- 
ity coniferous trees, 
such as the living 
firs, pines, larches, 
etc., gave rise for 
the most part to 
the mineral oils. 
The class of living 
coniferae is well 
known for the va- 
rious oils which it 
furnishes natural- 
ly, and for others 
which its represen- 
tatives yield on be- 
ing subjected to 
distillation. The 
gradually increas- 
ing amount of heat 
which we meet the 
deeper we go be- 
neath the surface, 
has been the cause 
of a slow and continuous distillation 




Fig. 2. — Annularia radiata. 
iferous sandstone. 



Carbon- 



whilst the 



*4 



THE STORY OF A PIECE OF COAL. 



oil so distilled has found its way to the surface in 
the shape of mineral-oil springs, or has accumu- 
lated in troughs in the strata, ready for use, to be 
drawn up when a well has been sunk into it. 

The plants which have gone to make up the 
coal are not at once apparent to the naked eye. 
We have to search among the shales and clays 
and sandstones which enclose the coal-seams, and 

in these we find petrified 
specimens which ena- 
ble us to build up in 
our mind pictures of the 
vegetable creation which 
formed the jungles and 
forests of these immense- 
ly remote ages, and 
which, densely packed 
together on the old for- 
est floor of those days, 
is now apparent to us as 
coal. 

A very large propor- 
tion of the plants which 
have been found in the 
coal-bearing strata con- 
sists of numerous spe- 
cies of ferns, the" num- 
ber of actual species 
which have been found 
preserved in the English 
coals being double the 
number now existing in 
Europe. The greater 
part of these do not 
seem to have been very much larger than our 
own living ferns, and, indeed, many of them bear 




FlG. 3. — Rhacopteris incequilat- 
era. Carboniferous limestone. 






THE ORIGIN AND COMPOSITION OF COAL. 15 



a close resemblance to some of our own living 
species. The impressions they have left on the 
shales of the coal-measures are most striking, and 
point to a time when the sandy clay which im- 
bedded them was borne by water in a very tran- 
quil manner, to be deposited where the ferns had 
grown, enveloping them gradually, and consoli- 
dating them into their mass of future shale. In 
one species known as the neuropteris, the nerves 
of the leaves are as clear and as apparent as in a 
newly-grown fern, the name being derived from 
two Greek words meaning " nerve-fern. " It is 
interesting to consider the history of such a leaf, 
throughout the ages that have elapsed since it 
was part of a living fern. First it grew up as a 
new frond, then gradually unfolded itself, and de- 
veloped into the perfect fern. Then it became 
cut off by the rising waters, and buried beneath 
an accumulation of sediment, and 
while momentous changes have 
gone on in connection with the 
surface of the earth, it has lain 
dormant in its hiding-place ex- 
actly as we see it, until now exca- 
vated with its contemporaneous 
vegetation, to form fuel for our 
winter fires. 

Although many of the ferns 
greatly resembled existing spe- 
cies, yet there were others in 
these ancient days utterly unlike 
anything indigenous to our coun- 
try now. There were undoubted tree-ferns, simi- 
lar to those which thrive now so luxuriously in 
the tropics, and which throw out their graceful 
crowns of ferns at the head of a naked stem, 




Fig. 4.— Frond of 
Pecopteris. Coal- 
shale. 



1 6 THE STORY OF A PIECE OF COAL. 

whilst on the bark are the marks at different 
levels of the points of attachment of former 
leaves. These have left in their places cicatrices 
or scars, showing the places from which they for- 
merly grew. Amongst the tree-ferns found are 
tnegaphyton, fialceopteris, and caulopteris, all of which 
have these marks upon them, thus proving that 




Fig. 5. — Pecopteris Serin. Coal-shale. 

at one time even tree-ferns had a habitat in our 
latitude. 

One form of tree-fern is known by the name 



THE ORIGIN AND COMPOSITION OF COAL. 17 



of Psaronius, and this was peculiar in the posses- 
sion of masses of aerial roots grouped round the 
stem. Some of the smaller species exhibit forms 
of leaves which are utterly unknown in the nomen- 
clature of living ferns. Most have had names as- 
signed to them in accordance with certain charac- 
teristics which they possess. This was the more 
possible since the fossilised impressions had been 
retained in so distinct a manner. Here before us 
is a specimen in a shale of pecopteris, as it is called, 
(pekos, a comb). The leaf in some species is not 
altogether unlike the well - known living fern 
osmunda. The position of the pinnules on both, 
sides of the central stalk are seen in the fossil to 
be shaped something like a comb, or a saw, whilst 
up the centre of each pinnule the vein is as promi- 
nent and noticeable as if 
the fern were but yester- 
day waving gracefully in 
the air, and but to-day 
imbedded in its shaly bed. 
Sphenopteris, or "wedge- 
fern," is the name ap- 
plied to another coal- 
fern ; gloss op teris, or 
"tongue-leaf " ; cyclopte- 
ris, or " round - leaf " ; 
odontopteris, or " tooth- 
leaf/' and many others, 
show their chief charac- 
teristics in the names 
which they individually 
bear. Alethopteris appears 
to have been the com- 
mon brake of the coal-period, and 
spects resembles pecopteris. 




Fig. 



6. — Sphenopteris affinis* 
Coal-shale. 



in some re- 



1 8 THE STORY OF A PIECE OF COAL. 

In some species of ferns so exact are the rep- 
resentations which they have impressed on the 
shale which contains them, that not only are the 
veins and nerves distinctly visible, but even the 
fructification still remains in the shape of the 
marks left by the so-called seeds on the backs of 
the leaves. Something more than a passing look 
at the coal specimens in a good museum will well 
repay the time so spent. 

What are known as septarian nodules, or 
snake-stones, are, at certain places, common in 
the carboniferous strata. They are composed of 
layers of ironstone and sandstone which have 
segregated around some central object, such as 
a fern-leaf or a shell. When the leaf of a fern 
has been found to be the central object, it has 
been noticed that the leaf can sometimes be sepa- 
rated from the stone in the form of a carbonace- 
ous film. 

Experiments were made many years ago by 
M. Goppert to illustrate the process of fossilisa- 
tion of ferns. Having placed some living ferns 
in a mass of clay and dried them, he exposed 
them to a red heat, and obtained thereby striking 
resemblances to fossil plants. According to the 
degree of heat to which they were subjected, the 
plants were found to be either brown, a shining 
black, or entirely lost. In the last mentioned 
case, only the impression remained, but the car- 
bonaceous matter had gone to stain the surround- 
ing clay black, thus indicating that the dark col- 
our of the coal-shales is due to the carbon derived 
from the plants which they included. 

Another very prominent member of the vege- 
tation of the coal-period, was that order of plants 
known as the Calamttes. The generic distinc- 






THE ORIGIN AND COMPOSITION OF COAL. 19 

tions between fossil and living ferns were so 
slight in many cases as to be almost indistin- 




FiG. 7. — Root of Catamites Suckowii. Coal-shale. 

guishable. This resemblance between the ancient 
and the modern is not found so apparent in other 
plants. The Calamites of the coal-measures bore 
indeed a very striking resemblance, and were 



20 



THE STORY OF A PIECE OF COAL. 



closely related, to our modern horse-tails, as the 
equiseta are popularly called; but in some respects 
they differed considerably. 

Most people are acquainted with the horse- 
tail (equiselum flu- 
viatile) of our 
marshes and ditch- 
es. It is a some- 
what graceful 
plant, and stands 
erect with a joint- 
ed stem. The fo- 
liage is arranged 
in whorls around 
the joints, and, 
unlike its fossil 
representatives, its 
joints are pro- 
tected by striated 
sheaths. The stem 
of the largest liv- 
ing species rarely 
exceeds half an 
inch in diameter, 
whilst that of the 
calamite attained 
a thickness of five 
inches. But the great point which is noticeable 
in the fossil calamites and equisetites is that they 
grew to a far greater height than any similar 
plant now living, sometimes being as much as 
eight feet high. In the nature of their stems, 
too, they exhibited a more highly organised ar- 
rangement than their living representatives, hav- 
ing, according to Dr. Williamson, a " fistular pith, 
an exogenous woody stem, and a thick smooth 




^x- 



FiG. %.—Calamocladus grandts. 
Carboniferous sandstone. 






THE ORIGIN AND COMPOSITION OF COAL. 21 

bark." The bark having almost always disap- 
peared has left the fluted stem known to us as 
the calamite. The foliage consisted of whorls of 
long narrow leaves, which differed only from the 
fern aster op hy Hit es in the fact that they were sin- 
gle-nerved. Sir William Dawson assigns the cala- 
mites to four sub-types: calamite proper, calamo- 
pitus, calamodendron, and enc alamo dendr on. 

Having used the word " exogenous," it might 
be as well to pay a little attention, in passing, to 
the nomenclature and broad classification of the 
various kinds of plants. We shall then doubtless 
find it far easier thoroughly to understand the 
position in the scale of organisation to which the 
coal plants are referable. 

The plants which are lowest in organisation 
are known as Cellular, since they are almost en- 
tirely composed of numerous cells built up one 




Fig. 9. — Asterophyllites foltosa. Coal-measures. 



-22 



THE STORY OF A PIECE pF COAL. 



above the other, and possess none of the higher 
forms of tissue and organisation which are met 
with elsewhere. This division includes the lich- 
ens, sea-weeds, confervae (green aquatic scum), 
fungi (mushrooms, dry-rot), &c. 

The division of Vascular plants includes the 
far larger proportion of vegetation, both living 
and fossil, and these plants are built up of vessels 
and tissues of various shapes and character. 

All plants are divided into (i) Cryptogams, or 
Flowerless, such as mosses, ferns, equisetums, (2) 
Phanerogams, or Flowering. Flowering plants 
are again divided into those with naked seeds, as 
the conifers and cycads (gymnosperms), and 
those whose seeds are enclosed in vessels, or ova- 
ries (angiosperms). 

Angiosperms are again divided into the mono- 
cotyledons, as the palms, and dicotyledons, which 
include most trees of temperate regions. 
Thus : — 



(M. A. Brongniart). 




(Lindley). 


Cellular 






Cryptogams (Flowerless) 


Fungi, seaweeds, 

li phpnc 


Thallogens 


Vascular 


IlL-llCIlb 




Cryptogams (Flowerless) 


Ferns, equisetums, 
mosses, lycopo- 
diums 


Acrogens 


Phanerogams (Flowering) 






Gymnosperms (having 


Conifers and cy- 


Gymnogens 


naked seeds) 


cads 




i. Dicotyledons 






Angiosperms (having 






enclosed seeds) 






i. Monocotyledons 


Palms, lilies, 
grasses 


Endogens 


ii. Dicotyledons 


Most European 
trees and shrubs 


Exogens 



THE ORIGIN AND COMPOSITION OF COAL. 23 



Adolphe Brongniart termed the coal era the 
•'Age of Acrogens," because, as we shall see, of 
the great predominance in those times of vascular 
cryptogamic plants, known in Dr. Lindley's no- 
menclature as "Acrogens." 

Two of these families have already been dealt 
with, viz., the ferns (filices), and the equisetums^ 
{catamites and 
eguisetites), and 
we now have to 
pass on to an- 
other family. 
This is that 
which includes 
the fossil repre- 
sentatives of the 
Lycopodiums, or 
Club - mosses, 
and which goes 
to make up in 
some coals as 
as two- 
of the 
mass. 



much 
thirds 
whole 




Fig. 10.- 



Sphenophyllum cuneifolium* 
Coal- shale. 

Everyone is 

more or less familiar with some of the living 
Lycopodiums, those delicate little fern-like mosses 
which are to be found in many a home. They 
are but lowly members of our present flora, and 
it may seem somewhat astounding at first sight 
that their remote ancestors occupied so important 
a position in the forests of the ancient period of 
which we are speaking. Some two hundred liv- 
ing species are known, most of them being con- 
fined to tropical climates. They are, as a rule, 
low creeping plants, although some few stand 



24 



THE STORY OF A PIECE OF COAL. 



erect. There is room for astonishment when we 
consider the fact that the fossil representatives of 
the family, known as Lepidodendra, attained a 
height of no less than fifty feet, and there is good 
ground for believing, in many cases, a far greater 
magnitude. They consist of long straight stems, 
or trunks which branch considerably near the top. 
These stems are covered with scars or scales, 
which have been caused by the separation of the 
petioles or leaf-stalks, and this gives rise to the 
name which the genus bears. The scars are ar- 
ranged in a spiral manner the whole of the way 
up the stem, and the stems often remain perfectly 
upright in the coal-mines, and reach into the 
strata which have accumulated 
above the coal-seam. 

Count Sternberg remarked 
that we are unacquainted with 
any existing species of plant, 
which like the Lepidodendron, pre- 
serves at all ages, and throughout 
the whole extent of the trunk, 
the scars formed by the attach- 
ment of the petioles, or leaf- 
stalks, or the markings of the 
leaves themselves. The yucca, 
dracaena, and palm, entirely shed 
their scales when they are dried 
up, and there only remain cir- 
cles, or rings, arranged round the 
trunk in different directions. The 
flabelliform palms preserve their 
scales at the inferior extremity 
of the trunk only, but lose them as they increase 
in age ; and the stem is entirely bare, from the 
middle to the superior extremity. In the ancient 




Fig. t i.— Cast of 
Lepidodendron in 
sandstone. 



THE ORIGIN AND COMPOSITION OF COAL. 25 




Fig. 



12.— Lepidodendron longifolium. 
Coal-shale. 



Lepidodendron, on the other hand, the more an- 
cient the scale of the leaf-stalk, the more appar- 
ent it still re- 
mains. Portions 
of stems have 
been discovered 
which contain 
leaf - scars far 
larger than those 
referred to above, 
and we deduce 
from these frag- 
ments the fact 
that those indi- 
viduals which 
have been found 
whole, are not by any means the largest of those 
which went to form so large a proportion of the 
ancient coal-forests. The lepidodendra bore linear 
one-nerved leaves, and the 
stems always branched di- 
chotomously and possessed 
a central pith. Specimens 
variously named knorria, 
lepidophloios, halonia, and telo- 
dendron are all referable to 
this family. 

In some strata, as for 
instance that of the Shrop- 
shire coal-field, quantities 
of elongated cylindrical 
bodies known as lepidostrobi 
have been found, which, it 
was early conjectured, were 
the fruit of the giant club-mosses about which we 
have just been speaking. Their appearance can 




Fig. 13. — Lepidodendron 
aculeatum in sandstone. 



26 



THE STORY OF A PIECE OF COAL. 



been found actually 



be called to mind by imagining the cylindrical 
fruit of the maize or Indian corn to be reduced to 
some three or four inches in length. The spo- 
rangia or cases which contained the microscopic 
spores or seeds were arranged around a central 
axis in a somewhat similar manner to that in 
which maize is found. These bodies have since 

situated at the end of 
branches of lepidodendron, 
thus placing their true 
nature beyond a doubt. 
The fossil seeds (spores) 
do not appear to have ex- 
ceeded in volume those 
of recent club-mosses, 
and this although the ac- 
tual trees themselves 
grew to a size very many 
times greater than the 
living species. This mi- 
nuteness of the seed- 
germs goes to explain the 
reason why, as Sir Charles 
Lyell remarked, the same 
species of lepidodendra are 
so widely distributed in 
the coal-measures of Eu- 
rope and America, their 
spores being capable of 
an easy transportation by the wind. 

One striking feature in connection with the 
fruit of the lepidodendron and other ancient repre- 
sentatives of the club-moss tribe, is that the bitu- 
minous coals in many, if not in most, instances, 
are made up almost entirely of their spores and 
spore-cases. Under a microscope a piece of such 




Fig. 14. — Lepidostrobus. 
Coal-shale. 



THE ORIGIN AND COMPOSITION OF COAL. 27 

coal is seen to be thronged with the minute 
rounded bodies of the spores interlacing one an- 
other and forming almost the whole mass, whilst 
larger than these, and often indeed enclosing 
them, are flattened bag-like bodies which are 
none other than the compressed sporangia which 
contained the former. 

Now, the little Scottish or Alpine club-moss. 
which is so familiar, produces its own little cones,. 




Fig. 15. — Lycopodites, Coal sandstone. 

each with its series of outside scales or leaves ; 
these are attached to the bags or spore-cases, 
which are crowded with spores. Although in 
miniature, yet it produces its fruit in just the 
same way, at the terminations of its little branches, 
and the spores, the actual germs of life, when ex- 
amined microscopically, are scarcely distinguish- 
able from those which are contained in certain 
bituminous coals. And, although ancient club- 
mosses have been found in a fossilised condition 
at least forty-nine feet high, the spores are no- 



28 THE STORY OF A PIECE OF COAL. 

larger than those of the miniature ciub-mosses of 
the present day. 

The spores are more or less composed of pure 
bitumen, and the bituminous nature of the coal 
depends largely on the presence or absence of 
these microscopic bodies in it. The spores of 
the living club-mosses contain so much resinous 
matter that they are now largely used in the 
making of fireworks, and upon the presence of 
this altered resinous matter in coal depends its 
capability of providing a good blazing coal. 

At first sight it seems almost impossible that 
such a minute cause should result in the forma- 
tion of huge masses of coal, such an inconceivable 
number of spores being necessary to make even 
the smallest fragment of coal. But if we look at 
the cloud of spores that can be shaken from a 
single spike of a club-moss, then imagine this to 
be repeated a thousand times from each branch 
of a fairly tall tree, and then finally picture a 
whole forest of such trees shedding in due sea- 
son their copious showers of spores to earth, we 
shall perhaps be less amazed than we were at first 
thought, at the stupendous result wrought out by 
so minute an object. 

Another well-known form of carboniferous 
vegetation is that known as the Sigillaria, and, 
connected with this form is one, which was long 
familiar under the name of Stigmaria, but which 
has since been satisfactorily proved to have 
formed the branching root of the sigillaria. The 
older geologists were in the habit of placing 
these plants among the tree-ferns, principally on 
account of the cicatrices which were left at the 
junctions of the leaf-stalks with the stem, after 
the former had fallen off. No foliage had, how- 



THE ORIGIN AND COMPOSITION OF COAL. 29 

ever, been met with which was actually attached 
to the plants, and hence, when it was discovered 
that some of them had long attenuated leaves 
not at all like those possessed by ferns, geologists 
were compelled to abandon this classification of 
them, and even now no satisfactory reference to 
existing orders of them has been made, owing to 
their anomalous structure. The stems are fluted 
from base to stem, although this is not so appar- 
ent near the base, whilst the raised prominences 
which now form the cicatrices, are arranged at 
regular distances within the vertical grooves. 

When they have remained standing for some 
length of time, and the strata have been allowed 
quietly to accumulate around the trunks, they 
have escaped compression. They were evident- 
ly, to a great extent, hollow like a reed, so that 
in those trees which still remain vertical, the in- 
terior has become filled up by a coat of sand- 
stone, whilst the bark has become transformed 
into an envelope of an inch, or half an inch of 
coal. But many are found lying in the strata in 
a horizontal plane. These have been cast down 
and covered up by an ever-increasing load of 
strata, so that the weight has, in the course of 
time, compressed the tree into simply the thick- 
ness of the double bark, that is, of the two 
opposite sides of the envelope which covered it 
when living. 

Sigillarice grew to a very great height without 
branching, some specimens having measured from 
60 to 70 feet long. In accordance with their 
outside markings, certain types are known as 
syringodendron, favularia, and dathraria. Dip- 
loxylon is a term applied to an interior stem ref- 
erable to the family. 



3o 



THE STORY OF A PIECE OF COAL. 



But the most interesting point about the 
sigillaricE is the root. This was for a long time 
regarded as an entirely distinct individual, and 
the older geologists explained it in their writings 




Fig. 16. — Stigmaria ficoides. Coal-shale. 

as a species of succulent aquatic plant, giving it 
the name of stig??iaria. They realized the fact 
that it was almost universally found in those beds 
which occur immediately beneath the coal-seams, 
but for a long time it did not strike them that it 
might possibly be the root of a tree. In an 
old edition of Lyell's " Element's of Geology," 
utterly unlike existing editions in quality, quan- 
tity, or comprehensiveness, after describing it as 
an extinct species of water-plant, the author 
hazarded the conjecture that it might ultimately 
be found to have a connection with some other 
well-known plant or tree. It was noticed that 
above the coal, in the roof, stigmariae were 
absent, and that the stems of trees which oc- 
curred there had become flattened by the weight 
of the overlying strata. The stigmariae, on 
the other hand, abounded in the underclay, as it 



THE ORIGIN AND COMPOSITION OF COAL. 31 

is called, and were not in any way compressed 
but retained what appeared to be their natural 
shape and position. Hence to explain their 
appearance, it was thought that they were water- 
plants, ramifying the mud in every direction, and 
finally becoming overwhelmed and covered by 
the mud itself. On botanical grounds, Brongniart 
and Lyell conjectured that they formed the roots 
of other trees, and this became the more appar- 
ent as it came to be acknowledged that the un- 
derclays were really ancient soils. All doubt 
was, however, finally dispelled by the discovery 
by Mr. Binney, of a sigillaria and a stigmaria in 
actual connection with each other, in the Lanca- 
shire coal-field. 

Stigmariae have since been found in the Cape 
Breton coal-field, attached to Lepidodendra, about 
which we have already spoken, and a similar dis- 
covery has since been made in the British coal- 
fields. This, therefore, would seem to show the 
affinity of the sigillaria to the lepidodendron, 
and through it to the living lycopods, or club- 
mosses. 

Some few species of stigmarian roots had been 
discovered, and various specific names had been 
given to them before their actual nature was 
made out. What for some time were thought to 
be long cylindrical leaves, have now been found 
to be simply rootlets, and in specimens where 
these have been removed, the surface of the stig- 
maria has been noticed to be covered with large 
numbers of protuberant tubercles, which have 
formed the bases of the rootlets. There appears 
to have also been some special kind of arrange- 
ment in their growth, since, unlike the roots of 
most living plants, the tubercles to which these 



32 



THE STORY OF A PIECE OF COAL. 




FIG. 17. — Section of stigmaria. 



rootlets were attached, were arranged spirally 
around the main root. Each of these tubercles 

was pitted in the 
centre, and into 
these the almost 
pointed ends of the 
rootlets fitted as by 
a ball and socket 
joint. 

U A single trunk 
of sigillaria in an 
erect forest pre- 
sents an epitome of 
a coal-seam Its 
roots represent the 
stigmaria under- 
clay ; its bark the 
compact coal ; its woody axis the mineral char- 
coal ; its fallen leaves and fruits, with remains of 
herbaceous plants growing in its shade, mixed 
with a little earthy matter, the layers of coarse 
coal. The condition of the durable outer bark of 
erect trees, concurs with the chemical theory of 
coal, in showing the especial suitableness of this 
kind of tissue for the production of the purer 
compact coals.'* — Dawson, " Structures in Coal." 
There is yet one other family of plants which 
must be mentioned, and which forms a very im- 
portant portion of the constituent flora of the coal- 
period. This is the great family of the coniferaz y 
which although differing in many respects from 
the highly organised dicotyledons of the present 
day, yet resembled them in some respects, espe- 
cially in the formation of an annual ring of woody 
growth. 

The conifers are those trees which, as the 



THE ORIGIN AND COMPOSITION OF COAL. 3$ 

name would imply, bear their fruit in the form 
of cones, such as the fir, larch, cedar, and others. 
The order is one which is familiar to all, not 
only on account of the cones they bear, and their 
sheddings, which in the autumn strew the ground 
with a soft carpet of long needle-like leaves, but 
also because of the gum-like secretion of resin 
which is contained in their tissues. Only a few 
species having been found in the coal-beds, and 
these, on examination under the microscope, have 
been discovered to be closely related to the arau- 
carian division of pines, rather than to any of 
our common firs. The living species of this 
tree is a native of Norfolk Island, in the Pacific, 
and here it attains a height of 200 feet, with a 
girth of 30 feet. From the peculiar arrangement 
of the ducts in the elongated cellular tissue of 
the tree, as seen under the microscope, the fossil 
conifers, which exhibit this structure, have been 
placed in the same division. 

The familiar fossil known to geologists as 
Sternbergia has now been shown to be the cast of 
the central pith of these conifers, amongst which 
may be mentioned cordaites, araucarites, and dad- 
oxylon. The central cores had become replaced 
with inorganic matter after the pith had shrunk 
and left the space empty. This shrinkage of the 
pith is a process which takes place in many plants 
even when living, and instances will at once occur, 
in which the stems of various species of shrubs 
when broken open exhibit the remains of the 
shrunken pith, in the shape of thin discs across 
the interval cavity. 

We might reasonably expect that where we 
find the remains of fossil coniferous trees, we 
should also meet with the cones or fruit which 



34 THE STORY OF A PIECE OF COAL. 

they bear. And such is the case. In some coal- 
districts fossil fruits, named cardiocarpum and 
trigonocarpum, have been found in great quanti- 
ties, and these have now been decided by bot- 
anists to be the fruits of certain conifers, allied, 
not to those which bear hard cones, but to those 
which bear solitary fleshy fruits. Sir Charles 
Lyell referred them to a Chinese genus of the 
yew tribe called salisburia. Dawson states that 
they are very similar to both taxus and salisburia. 
They are abundant in some coal-measures, and 
are contained, not only in the coal itself, but also 
in the sandstones and shales. The under-clays 
appear to be devoid of them, and this is, of course, 
exactly what might have been expected, since the 
seeds would remain upon the soil until covered up 
by vegetable matter, but would never form part 
of the clay soil itself. 

In connection with the varieties which have 
been distinguished in the families of the conifers, 
calamites, and sigillariae, Sir William Dawson 
makes the following observations: "I believe 
that there was a considerably wide range of or- 
ganisation in cordaitince as well as in calainites and 
sigillarice, and that it will eventually be found that 
there were three lines of connection between the 
higher cryptogams (flowerless) and the phaeno- 
gams (flowering), one leading from the lycopodes 
by the sigillarice, another leading by the cordaites, 
and the third leading from the equisetums by the 
xalamites. Still further back the characters, after- 
wards separated in the club-mosses, mare's-tails,« 
and ferns, were united in the rhizocarps, or, as 
•some prefer to call them, the heterosporous filu 
<eincd" 

In concluding this chapter dealing with the 



THE ORIGIN AND COMPOSITION OF COAL. 35 

various kinds of plants which have been discov- 
ered as contributing to the formation of coal- 
measures, it would be as well to say a word or 
two concerning the climate which must have been 
necessary to permit of the growth of such an 
abundance of vegetation. It is at once admitted 
by all botanists that a moist and quite warm at- 
mosphere was necessary to account for the exist- 
ence of such an abundance of ferns. The gor- 
geous waving tree-ferns which were doubtless an 
important feature of the landscape, would have 
required a moist heat such as does not now exist 
in this latitude, although not necessarily a trop- 
ical heat. The magnificent giant lycopodiums 
cast into the shade all our living members of that 
class, the largest of which perhaps are those that 
flourish in New Zealand. In New Zealand, too, 
are found many species of ferns, both those which 
are arborescent and those which are of more hum- 
ble stature. Add to these the numerous conifers 
which are there found, and we shall find that a • 
forest in that country may represent to a certain 
extent the appearance presented by a forest of 
carboniferous vegetation. The ferns, lycopods, 
and pines, however, which appear there, it is but 
fair to add, are mixed with other types allied to 
more recent forms of vegetation. 

There are many reasons for believing that the 
amount of carbonic acid gas then existing in the 
atmosphere was larger than the quantity which 
we now find, and Professor Tyndall has shown 
that the effect of this would be to prevent radia- 
tion of heat from the earth. The resulting forms 
of vegetation would be such as would be com- 
parable with those which are now reared in the 
green-house or conservatory in these latitudes. 



$6 THE STORY OF A PIECE OF COAL. 

The gas would, in fact, act as a glass roof, ex- 
tending over the whole world. 



CHAPTER II. 

A GENERAL VIEW OF THE COAL-BEARING STRATA. 

In considering the source whence coal is de- 
rived, we must be careful to remember that coal 
itself is but a minor portion of the whole forma- 
tion in which it occurs. The presence of coal has 
indeed given the name to the formation, the word 
" carboniferous " meaning "coal-bearing," but in 
taking a comprehensive view of the position which 
it occupies in the bowels of the earth, it will be 
necessary to take into consideration the strata in 
which it is found, and the conditions, so far as are 
known, under which these were deposited. 

Geologically speaking, the Carboniferous for- 
mation occurs near the close of that group of sys- 
tems which have been classed as "palaeozoic," 
younger in point of age than the well-known De- 
vonian and Old Red Sandstone strata, but older 
by far than the Oolites, the Wealden, or the Cre- 
taceous strata. 

^^ In South Wales the coal-bearing strata have 
been estimated at between n,ooo and 12,000 feet, 
yet amongst this enormous thickness of strata, the 
whole of the various coal-seams, if taken together, 
probably does not amount to more than 120 feet. 
This great disproportion between the total thick- 
ness and the thickness of coal itself shows itself 
in every coal-field that has been worked. The 
thickness of single seams varies from that of a 



GENERAL VIEW OF COAL-BEARING STRATA. 37 

knife-blade to over a hundred feet, the largest of 
these occurring in Pennsylvania and Southern 
France. Those over eight or ten feet are almost 
always compound seams — that is, they consist of 
two or more seams or " benches " separated by 
thin " partings," which represent thicker strata 
of clay or sandstone that have thinned out. 

It is not possible, therefore, to realise complete- 
ly the significance of the coal-beds themselves un- 
less there is also a knowledge of the remaining 
constituents of the whole formation. The strata 
found in the various coal-fields differ considerably 
amongst themselves in character. There are, 
however, certain well-defined characteristics which 
find representation in most of the principal coal- 
fields. 

The following list, condensed from reports by 
J. J. Stevenson and H. M. Chance, gives a gen- 
eral idea of the association of strata in Western 
Pennsylvania : 

Upper Barren Series, or Permian Beds. 

Alternating beds of limestone, sandstone, 
and shale, with one or two feet in a 
hundred of coal, and iron ore in some 
localities. 

Upper Productive Coal Series, or Monon- 
gahela River Series. 

Shale, sandstone, limestone, and fire-clay 
alternating with coal-beds which may 
reach a proportion of 1 in 20. 

Lower Barren Coal-measures. 

Connellsville, Morgantown, and Mahoning 
sandstones, shale, black and crinoidal 
limestone, fire-clay and coal. 



38 THE STORY OF A PIECE OF COAL. 

Lower Productive Coal-measures, or Al- 
leghany River Series : 

Fire-clay, Freeport limestone, shale, sand- 
stone, brick-clay, and slate in about the 
same proportion with coal as in the Up- 
per Productive Series. 

Pottsville conglomerate, or millstone grit. 

Layers of clay-ironstone are often in the series. 

In the Pennsylvania anthracite region about 
the same formations alternate, except that lime- 
stone is absent. 

In short, the formation consists of masses of 
sandstone, shale, limestone, and coal, these also 
enclosing clays and ironstones, and, in the lime- 
stone, marbles and veins of the ores of lead, 
zinc, and antimony, and occasionally silver. 

Each of the principal divisions has its repre- 
sentative in Great Britain, Belgium, and Ireland, 
but, unfortunately for the last-named country, 
the whole of the upper productive-measures are 
there absent. It is from these measures that 
almost all our commercial coals are obtained. 

As the most apparent of the rocks of the sys- 
tem are sandstone, shale, limestone, and coal, it 
will be necessary to consider how these were de- 
posited in the waters of the carboniferous ages, 
and this we can best do by considering the laws 
under which strata of a similar nature are now 
being deposited as sedimentary beds. 

A great proportion consists of sandstone. 
Now sandstone is the result of sand which has 
been deposited in large quantities, having be- 
come indurated or hardened by various processes 
brought to bear upon it. It is necessary, there- 
fore, first to ascertain whence came the sand, and 



GENERAL VIEW OF COAL-BEARING STRATA. 39 

whether there are any peculiarities in its method 
of deposition which will explain its stratification. 
It will be noticed at once that it bears a considera- 
ble amount of evidence of what is called " current- 




Fig. 18.- 



-Sigillarian trunks in current-bedded sandstone. 
St. Etienne. 



bedding/' that is to say, that the strata, instead of 
being regularly deposited, exhibit series of wedge- 
shaped masses, which are constantly thinning out. 
Sand and quartz are of the same chemical 
composition, and in all probability the sand of 
which every sandstone in existence is composed, 
appeared on this earth in its first solid form in the 
shape of quartz. Now quartz is a comparatively 
heavy mineral, so also, therefore, will sand be. 
It is also very hard, and in these two respects it 
differs entirely from another product of sedimen- 
tary deposition, namely, mud or clay, with which 



40 THE STORY OF A PIECE OF COAL. 

we shall have presently to deal when coming to 
the shales. Since quartz is a hard mineral, it 
necessarily follows that it will suffer, without 
being greatly affected, a far greater amount of 
wearing and knocking about when being trans- 
ported by the agency of currents and rivers, than 
will a softer substance, such as clay. An equal 
amount of this wearing action upon clay will re- 
duce it to a fine impalpable silt. The grains of 
sand, however, will still remain of an appreciable 
average size, and where both sand and clay are 
being transported to the sea in one and the same 
stream, the clay will be transported to long dis- 
tances, whilst the sand, being heavier, bulk for 
bulk, and also consisting of grains larger in size 
than grains of clay, will be rapidly deposited, and 
form beds of sand. Of course, if the current be 
a violent one, the sand is transported, not by 
being held in suspension, but rather by being 
pushed along the bed of the river ; such an action 
will then tend to cause the sand to become pow- 
dered into still finer sand. 

When a river enters a sea it soon loses its in- 
dividuality ; it becomes merged in the body of 
the ocean, where it loses its current, and where 
therefore it has no power to keep in suspension 
the sediment which it had brought down from 
the higher lands. When this is the case, the sand 
borne in suspension is the first to be deposited, 
and this accumulates in banks near the entrance 
of the river into the sea. We will suppose, for 
illustration, that a small river has become charged 
with a supply of sand. As it gradually approaches 
the sea, and the current loses its force, the sand 
is the more sluggishly carried along, until finally 
it falls to the bottom, and forms a layer of sand 



GENERAL VIEW OF COAL-BEARING STRATA. 4 1 

there. This layer increases in thickness until it 
causes the depth of water above it to become 
comparatively shallow. On the shallowing proc- 
ess taking place, the current will still have a 
certain, though slighter, hold on the sand in sus- 
pension, and will transport it yet a little further 
seaward, when it will be thrown down at the edge 
of the bank or layer already formed, thus tend- 
ing to extend the bank, and to shallow a wider 
space of river-bed. 

As a result of this action, strata would be 
formed, showing stratification diagonally as well 
as horizontally, represented in section as a num- 
ber of banks which had seemingly been thrown 
down one above the other, ending in thin wedge- 
shaped terminations where the particular supply 
of sediment to which each owed its formation 
had failed. 

The masses of sandstone which are found in 
the carboniferous formation, exhibit in a large 
degree these wedge-shaped strata, and we have 
therefore a clue at once, both as to their propin- 
quity to sea and land, and also as to the manner 
in which they were formed. 

There is one thing more, too, about them. 
Just as, in the case we were considering, we could 
observe that the wedge-shaped strata always 
pointed away from the source of the material 
which formed them, so we can similarly judge 
that in the carboniferous strata the same deduc- 
tion holds good, that the diagonally-pointing 
strata were formed in the same way> and that 
their thinning out was simply owing to tempo- 
rary failure of sediment, made good, however, by 
a further deposition of strata when the next sup- 
ply was borne down. 




42 THE STORY OF A PIECE OF COAL. 

It is scarcely likely, however, that sand in a 
pure state was always carried down by the cur- 
rents to the sea. Some- 
times there would be 
some silt mixed with it. 
Just as in many parts 
large masses of almost 
pure sandstone have 
been formed, so in 
other places shales, or, 
as they are popularly 

TIG. ig.-Productus. ^ W ?„ b Z mi ? erS ' 

Coal-measures. bind, have been 

vj formed. \; Shales are 

formed from the clays which have been carried 
down by the rivers in the shape of silt, but which 
have since become hardened, and now split up 
easily into thin parallel layers. The reader has 
no doubt often handled a piece of hard clay when 
fresh from the quarry, and has remembered how 
that, when he has been breaking it up, in order, 
perhaps, to excavate a partially hidden fossil, it 
has readily split up in thin flakes or layers of 
shaly substance. This exhibits, on a small scale, 
the chief peculiarity of the coal shales. 

The formation of shales will now demand our 
attention. When a river is carrying down "with it 
a quantity of mud or clay, it is transported as a 
fine, dusty silt, and when present in quantities, 
gives the muddy tint to the water which is so no- 
ticeable. We can very well see how that silt will 
be carried down in greater quantities than sand, 
since nearly all rivers in some part of their 
course will travel through a clayey district, and 
finely divided clay, being of a very light nature, 
will be carried forward whenever a river passes 



GENERAL VIEW OF COAL-BEARING STRATA. 43, 

pver such a district. And a very slight current 
being sufficient to carry it in a state of suspen- 
sion, it follows that it will have little opportunity 
of falling to the bottom, until, by some means or 
other, the current, which is the means of its con- 
veyance, becomes stopped or hindered consider- 
ably in its flow. 

When the river enters a large body of water,, 
such as the ocean or a lake, in losing its individ- 
uality, it loses also the velocity of its current,, 
and the silt tends to sink down to the bottom. 
But being less heavy than the sand, about which 
we have previously spoken, it does not sink all at 
once, but partly with the impetus it has gained,, 
and partly on account of the very slight velocity 
which the current still retains, even after having" 
entered the sea, it will be carried out some dis- 
tance, and will the more gradually sink to the 
bottom. The deeper the water in which it falls 
the greater the possibility of its drifting farther 
still, since in sinking, it would fall, not vertically, 
but rather as the drops of rain in a shower when 
being driven before a gale of wind. Thus we 
should notice that clays and shales would exhibit 
a regularity and uniformity of deposition over a 
wide area. Currents and tides in the sea or lake 
would tend still further to retard deposition, 
whilst any stoppages in the supply of silt which 
took place would give the former layer time to 
consolidate and harden, and this would assist in 
giving it that bedded structure which is so no- 
ticeable in the shales, and which causes it to 
split up into fine laminae. This uniformity of 
structure in the shales over wide areas is a well- 
ascertained characteristic of the coal-shales, and 
we may therefore regard the method of their 



44 THE STORY OF A PIECE OF COAL. 

deposition as given here with a degree of cer- 
tainty. 

There is a class of deposit found among the 
coal-beds, which is known as the " underclay," 
and this is the most regular of all as to the posi- 
tion in which it is found. The underclays are 
found beneath every bed of coal. ' k Warrant," 
" spavin," and " gannister " are local names which 
are applied to it in England, the last term being 
used when the clay contains such a large propor- 
tion of silicious matter as to become almost like 
a hard flinty rock. Sometimes, however, it is a 
soft clay, at others it is mixed with sand, but 
whatever the composition of the underclays may 
be, they always agree in being unstratified. They 
also agree in this respect that the peculiar fossils 
known as stigmarice abound in them, and in some 
cases to such an extent that the clay is one thickly 
matted mass of the filamentous rootlets of these 
fossils. We have seen how these gradually came 
to be recognised as the roots of trees which grew 
in this age, and whose remains have subsequently 
become metamorphosed into coal, and it is but 
one step farther to come to the conclusion that 
these underclays are the ancient soils in which 
the plants grew. 

No sketch of the various beds which go to 
form the coal-measures would be complete which 
did not take into account the enormous beds of 
mountain limestone which form the basis of the 
whole system, and which in thinner bands are 
intercalated amongst the upper portion of the 
system, or the true coal-measures. 

Now, limestones are not formed in the same 
way in which we have seen that sandstones and 
shales are formed. The last two mentioned owe 



GENERAL VIEW OF COAL-BEARING STRATA. 45 



their origin to their deposition as sediment in 
seas, estuaries, or lakes, but the masses of lime- 
stone which are found in the various geological 
formations owe their origin to 
causes other than that of sedi- 
mentary deposition. 

In carboniferous times there 
lived numberless creatures which 
we know nowadays as encrinites. 
These, when growing, were fixed 
to the bed of the ocean, and ex- 
tended upward in the shape of 
pliant stems composed of lime- 
stone joints or plates; the Jf stem °f 
each encrinite then ex- jcf ^0'^ panded 
at the top in the shape bJ0^ °f a & or " 
geous and graceful star- J^jps» fish, pos- 
sessed of 
numberless 
and lengthy arms. 
These encrinites 
grew in such pro- 
fusion that after 
death, when the 
plates of which their stems consisted, became 
loosened and scattered over the bed of the sea, 
they accumulated and formed solid beds of lime- 
stone. Besides the encrinites, there were of course 
other creatures which were able to create the hard 
parts of their structures by withdrawing lime 
from the sea, such as forarninifera, shell-fish, and 
especially corals, so that all these assisted after 
death in the accumulation of beds of limestone 
where they had grown and lived. 

There is one peculiarity in connection with 
the habitats of the encrinites and corals which 



Fig. 20. — Encrinite. 



4 6 



THE STORY OF A PIECE OF COAL. 



goes some distance in supplying us with a useful 
clue as to the conditions under which this portion 
of the carboniferous formation was formed. 
These creatures find it a difficult matter, as a 
rule, to live and secrete their calcareous skeleton 
in any water but that which is clear, and free 
from muddy or sandy sediment. They are there- 
fore not found, 
generally speak- 
ing, where the oth- 
er deposits which 
we have consid- 
ered, are forming, 
and, as these are 
always found near 
the coasts, it fol- 
lows that the habi- 
tats of the crea- 
tures referred to 
must be far out at 
sea where no mud- 
dy sediments, borne by rivers, can reach them. 
We can therefore safely come to the conclusion 
that the large masses of encrinital limestone, 
which attain such an enormous thickness in some 
places, especially in Ireland, have been formed far 
away from the land of the period ; we can at the 
same time draw the conclusion that if we find the 
encrinites broken and snapped asunder, and the 
limestone deposits becoming impure through be- 
ing mingled with a proportion of clayey or sandy 
deposits, that we are approaching a coast-line 
where perhaps a river opened out, and where it 
destroyed the growth of encrinites, mixing with 
their dead remains the sedimentary debris of the 
land. 




Fig. 21. — Encrinital limestone. 



GENERAL VIEW OF COAL-BEARING STRATA. 47 

We have lightly glanced at the circumstances 
attending the deposition of each of the principal 
rocks which form the beds amongst which coal is 
found, and have now to deal with the formation 
of the coal itself. We have already considered 
the various kinds of plants and trees which have 




Fig. 22. — Encrinites : various. Mountain limestone. 



been discovered as contributing their remains to 
the formation of coal, and have now to attempt 
an explanation of how it came to be formed in so 
regular a manner over so wide an area. 

Few countries are entirely without coal. The 
United States has by far the largest fields, amount- 
ing to about 190,000 square miles. There are 
something like 12,000 square miles in the British 
Isles, and deposits of considerable extent are 
found on the continent of Europe, in Asia, 
Australia, and South America. And yet, spread 
over them, we find a series of beds of coal which 



48 THE STORY OF A PIECE OF COAL. 

in many cases extend throughout the whole area 
with apparent regularity. If we take it, as there 
seems every reason to believe was the case, that 
almost all these coal-fields were not only being 
formed at the same time, but were in most in- 
stances in continuation with one another, this 
regularity of deposition of comparatively narrow 
beds of coal, appears all the more remarkable. 

The question at once suggests itself, Which of 
two things is probable ? Are we to believe that 
all this vegetable matter was brought down by 
some mighty river and deposited in its delta, or 
that the coal-plants grew just where we now find 
the coal ? 

Formerly it was supposed that coal was 
formed out of dead leaves and trees, the refuse of 
the vegetation of the land, which had been car- 
ried down by rivers into the sea and depositee! at 
their mouths, in the same way that sand and mud, 
as we have seen, are swept down and deposited. 
If this were so, the extent of the deposits would 
require a river with an enormous embouchure, 
and we should be scarcely warranted in believing 
that such peaceful conditions would there prevail 
as to allow of the layers of coal to be laid down 
with so little disturbance and with such regularity 
over these wide areas. But the great objection 
to this theory is, that not only do the remains 
still retain their perfection of structure, but they 
are comparatively pure — i. <?., unmixed with sedi- 
mentary depositions of clay or sand. Now, rivers 
would not bring down the dead vegetation alone ; 
their usual burden of sediment would also be de- 
posited at their mouths, and thus dead plants, 
sand, and clay would be mixed up together in 
one black shaly or sandy mass, a mixture which 



GENERAL VIEW OF COAL-BEARING STRATA. 49 

would be useless for purposes of combustion. 
The only theory which explained all the recog- 
nised phenomena of the coal-measures was that 
the plants forming the coal actually grew where 
the coal was formed, and where, indeed, we now 
find it. When the plants and trees died, their re- 
mains fell to the ground of the forest, and these 
soon turned to a black, pasty, vegetable mass, 
the layer thus formed being regularly increased 
year by year by the continual accumulation of 
fresh carbonaceous matter. By this means a bed 
would be formed with regularity over a wide 
area; the coal would be almost free from an ad- 
mixture of sandy or clayey sediment, and prob- 
ably the rate of formation would be no more 
rapid in one part of the forest than another. 
Thus there would be everywhere uniformity of 
thickness. The warm and humid atmosphere, 
which it is probable then existed, would not 
only have tended towards the production of 
an abnormal vegetation, but would have assisted 
in the decaying and disintegrating processes 
which went on amongst the shed leaves and 
trees. 

When at last it was announced as a patent 
fact that every bed of coal possessed its under- 
clay, and that trees had been discovered actually 
standing upon their own roots in the clay, there 
was no room at all for doubt that the correct 
theory had been hit upon — viz., that coal is now 
found just where the trees composing it had 
grown in the past. 

But we have more than one coal-seam to 

account for. We have to explain the existence 

of several layers of coal which have been formed 

over one another on the same spot at successive 

4 



50 THE STORY OF A PIECE OF COAL. 

periods, divided by other periods when shale and 
•sandstones only have been formed. 

A careful estimate of the Lancashire coal-field 
has been made by Professor Hull for the British 
Geological Survey. Of the 7000 feet of carbonif- 
erous strata here found, spread out over an area 
of 217 square miles, there are on the average 
eighteen seams of coal. 

This is only an instance of what is to be found 
elsewhere. Eighteen coal-seams ! what does this 
mean ? It means that, during carboniferous times, 
on no less than eighteen occasions, separate and 
distinct forests have grown on this self-same spot, 
and that between each of these occasions changes 
have taken place which have brought it beneath 
the waters of the ocean, where the sandstones 
and shales have been formed w T hich divide the 
coal-seams from each other. We are met here 
by a wonderful demonstration of the instability 
of the surface of the earth, and we have to do 
our best to show how the changes of level have 
been brought about, which have allowed of this 
game of geological see-saw to take place between 
sea and land. Changes of level ! Many a hard 
geological nut has only been overcome by the 
application of the principle of. changes of level 
in the surface of the earth, and in this we shall 
find a sure explanation of the phenomena of the 
•coal-measures. 

Great changes of the level of the land are 
undoubtedly taking place even now on the 
earth's surface, and in assuming that similar 
changes took place in carboniferous times, we 
shall not be assuming the former existence of 
.an agent with which we are now unfamiliar. 
And when we consider the thicknesses of sand- 



GENERAL VIEW OF COAL-BEARING STRATA. 5 1 

stone and shale which intervene beneath the 
coal-seams, we can realise to a certain extent 
the vast lapses of years which must have taken 
place between the existence of each forest ; so 
that although now an individual passing up a 
coal-mine shaft may rapidly pass through the 
remains of one forest after another, the rise of 
the strata above each forest-bed then was tre- 
mendously slow, and the period between the 
growth of each forest must represent the passing 
away of countless ages. Perhaps it would not 
be too much to say that the strata between 
some of the coal-seams would represent a period 
not less than that between the formation of the 
few tertiary coals with which we are acquainted, 
and a time which is still to us in the far-away 
future. 

The actual seams of coal themselves will not 
yield much information, from which it will be 
possible to judge of the contour of the land- 
masses of this ancient period. Of one thing 
we are sure, namely, that at the time each seam 
was formed, the spot where it accumulated was 
dry land. If, therefore, the seams which appear 
one above the other coincide fairly well as to 
their superficial extent, we can conclude that 
each time the land was raised above the sea 
and the forest again grew, the contour of the 
land was very similar. The conclusion will be 
very useful to go upon, since whatever decision 
may be come to as an explanation of one suc- 
cessive land-period and sea-period on the same 
spot, will be applicable to the eighteen or more 
periods necessary for the completion of some of 
the coal-fields. 

We will therefore look at one of the sandstone 



52 THE STORY OF A PIECE OF COAL. 

masses which occur between the coal-seams, and 
learn what lessons these have to teach us. In 
considering the formation of strata of sand in the 
seas around our river-mouths, it was seen that, 
owing to the greater weight of the particles of 
the sand over those of clay, the former the 
more readily sank to the bottom, and formed 
banks not very far away from the land. It was 
seen, too, that each successive deposition of sand 
formed a wedge-shaped layer, with the point of 
the wedge pointing away from the source of 
origin of the sediment, and therefore of the cur- 
rent which conveyed the sediment. Therefore, 
if in thQ coal-measure sandstones the layers were 
found with their wedges all pointing in one di- 
rection, we should be able to judge that the 
currents were all from one -direction, and that, 
therefore, they were formed by a single river. 
But this is just what we do not find, for instead 
of it the direction of the wedge-shaped strata 
varies in almost every layer, and the current- 
bedding has been brought about by currents 
travelling in every direction. Such diverse 
current-bedding could only result from the fact 
that the spot where the sand was laid down was 
subject to currents from every direction, and 
the inference is that it was well within the 
sphere of influence of numerous streams and 
rivers, which flowed from every direction. The 
only condition of things which would explain 
this is that the sandstone was originally formed 
in a closed sea or large lake, into which numer- 
ous rivers flowing from every direction poured 
their contents. 

Now, in the sandstones, the remains of numer- 
ous plants have been found, but they do not pre- 



GENERAL VIEW OF COAL-BEARING STRATA. 53 

sent the perfect appearance that they do when 
found in the shales ; in fact they appear to have 
suffered a certain amount of damage through 
having drifted some distance. This, together 
with the fact that sandstones are not formed 
far out at sea, justify the safe conclusion that 
the land could not have been far off. Wherever 
the current-bedding shows itself in this manner 
we may be sure we are examining a spot from 
which the land in every direction could not have 
been at a very great distance, and also that, 
since the heavy materials of which sandstone is 
composed could only be transported by being 
impelled along by currents at the bed of the sea, 
and that in deep water such currents could not 
exist, therefore we may safely decide that the 
sea into which the rivers fell was a comparatively 
shallow one. 

Although the present coal-fields of England 
are divided from one another by patches of other 
beds, it is probable that some of them were for- 
merly connected with others, and a very wide 
sheet of coal on each occasion was laid down. 
The question arises as to what was the extent 
of the inland sea or lake, and did it include the 
area covered by the coal basins of Scotland and 
Ireland, of France and Belgium ? And if these, 
why not those of America and other parts ? 
The deposition of the coal, according to the the- 
ory here advanced, may as well have been brought 
about in a series of large inland seas and lakes, 
as by one large comprehensive sea, and probably 
the former is the more satisfactory explanation 
of the two. But the astonishing part of it is 
that the changes in the level of the land must 
have been taking place simultaneously over thesa 



54 THE STORY OF A PIECE OF COAL. 

large areas, although, of course, while one quar- 
ter may have been depressed beneath the sea, 
another may have been raised above it. 

In connection with the question of the con- 
tour of the land during the existence of the large 
lakes or inland seas, Professor Hull has prepared, 
in his series of maps illustrative of the Palaeo- 
Geography of the British Islands, a map show- 
ing on incontestible grounds the existence during 
the coal-ages of a great central barrier or ridge 
of high land stretching across from Anglesea, 
south of Flint, Staffordshire, and Shropshire coal- 
fields, to the eastern coast of Norfolk. He re- 
gards the British coal-measures as having been 
laid down in two, or at most three, areas of dep- 
osition — one south of this ridge, the remainder 
to the north of it. In regard to the extent of 
the former deposits of coal in Ireland, there is 
every probability that the sister island was just 
as favourably treated in this respect as Great 
Britain. Most unfortunately, Ireland has since 
suffered extreme denudation, notably from the 
great convulsions of nature at the close of the 
very period of their deposition, as well as in more 
recent times, resulting in the removal of nearly 
all the valuable upper carboniferous beds, and 
leaving only the few unimportant coal-beds to 
which reference has been made. 

We are unable to believe in the continuity of 
the English and American coal-beds, for the 
great source of sediment in those times was a 
continent situated on the site of the Atlantic 
Ocean, and it is owing to this extensive continent 
that the forms of flora found in the coal-beds in 
each country bear so close a resemblance to one 
another, and also that the encrinital limestone 



GENERAL VIEW OF COAL-BEARING STRATA. 55 




Fig. ^.—Cyatho- 
phyllum. Coral in 
encrinital limestone- 



which was formed in the purer depths of the 
ocean on the east, became mixed with silt, and 
formed masses of shaly impure 
limestone in the south-western 
parts of Ireland. 

It must be noted that, al- 
though we may attribute to up- 
heaval from beneath the fact that 
the bed of the sea became tem- 
porarily raised at each period in- 
to dry land, the deposits of sand 
or shale would at the same time 
be tending to shallow the bed, 
and this alone would assist the 
process of upheaval by bringing 
the land at least very near to the 
surface of the water. 

Each upheaval, however, 
could have been but a temporary arrest of the 
great movement of crust subsidence which was. 
going on throughout the coal-period, so that, at 
its close, when the last coal-forest grew upon the 
surface of the land, there had disappeared, in the 
case of South Wales, a thickness of 11,000 feet of 
material. 

Of the many remarkable things in connection 
with coal-beds, not the least is the state of purity 
in which coal is found. On the floor of each 
forest there would be many a streamlet or even 
small river which would wend its way to meet 
the not very distant sea, and it is surprising at 
first that so little sediment found its way into the 
coal itself. But this was cleverly explained by 
Sir Charles Lyell, who noticed, on one of his 
visits to America, that the water of the Missis- 
sippi, around the rank growths of cypress which 



56 THE STORY OF A PIECE OF COAL. 

form the "cypress swamps " at the mouths of 
that river, was highly charged with sediment, but 
that, having passed through the close under- 
growth of the swamps it issued in almost a pure 
state, the sediment which it bore having been 
filtered out of it and precipitated. This very sat- 
isfactorily explained how in some places carbon- 
aceous matter might be deposited in a perfectly 
pure state, whilst in others, where sandstone or 
shale was actually forming, it might be impreg- 
nated by coaly matter in such a way as to cause 
it to be stained black. In times of flood sediment 
would be brought in, even where pure coal had 
been forming, and then we should have a thin 
" parting " of sandstone or shale, which was 
formed when the flood was at its height. Or a 
slight sinking of the land might occur, in which 
case also the formation of coal would temporarily 
cease, and a parting of foreign matter would be 
formed, which, on further upheaval taking place, 
would again give way to another forest growth. 
Some of the thicker beds have been found pre- 
senting this aspect, such as the South Stafford- 
shire ten-yard coal, which in some parts splits up 
into a dozen or so smaller beds, with partings of 
sediment between them. 

In the face of the stupendous movements 
which must have happened in order to bring 
about the successive growth of forests one above 
another on the same spot, the question at once 
arises as to how these movements of the solid 
earth came about, and what was the cause which 
operated in such a manner. We can only judge 
that, in some way or other, heat, or the with- 
drawal of heat, has been the prime motive power. 
We can perceive, from what is now going on in 



GENERAL VIEW OF COAL-BEARING STRATA. 57 

some parts of the earth, how great an influence it 
has had in shaping the land, for volcanoes owe 
their activity to the hidden heat in the earth's 
interior, and afford us an idea of the power of 
which heat is capable in the matter of building 
up and destroying continents. No less certain is 
it that heat is the prime factor in those more 
gradual vertical movements of the land to which 
we have referred elsewhere, but in regard to the 
exact manner in which it acts we are very much 
in the dark. Everybody knows that, in the ma- 
jority of instances, material substances of all 
kinds expand under the influence of heat, and 
contract when the source of heat is withdrawn. 
If we can imagine movements in the quantity of 
heat contained in the solid crust, the explanation 
is easy, for if a certain tract of land receive an 
accession of heat beneath it, it is certain that the 
principal effect will be an elevation of the land, 
consequent on the expansion of its materials, with 
a subsequent depression when the heat beneath 
the tract in question becomes gradually lessened. 
Should the heat be retained for a long period, the 
strata would be so uplifted as to form an anti- 
clinal, or saddle-back, and then, should subse- 
quent denudation take place, more ancient strata 
would be brought to view. Denudation has in 
fact carried away much of the upper portion of 
all coal-bearing strata, whether upheaved or hori- 
zontal, so that in many localities as in northern 
Pennsylvania the coal is left in isolated patches 
which may form either mountains or basins. 

How the heat-waves act, and the laws, if any, 
which they obey in their subterranean movements, 
we are unable to judge. From the properties 
which heat possesses we know that its presence 



58 THE STORY OF A PIECE OF COAL. 

or absence produces marked differences in the 
positions of the strata of the earth, and from 
observations made in connection with the closing 
of some volcanoes, and the opening up of fresh 
earth-vents, we have gone a long way towards 
establishing the probability that there are even 
now slow and ponderous movements taking place 
in the heat stored in the earth's crust, whose 
effects are appreciably communicated to the out- 
side of the thin rind of solid earth upon which we 
live. 

Owing to the great igneous and volcanic ac- 
tivity at the close of the deposition of the car- 
boniferous system of strata, the coal-measures 
exhibit what are known as faults in abundance. 
The mountain limestone, where it outcrops at the 
surface, is observed to be much jointed, so much 
so that the work of quarrying the limestone is 
greatly assisted by the jointed structure of the 
rock. Faults differ from joints in that, whilst 
the strata in the latter are still in relative posi- 
tion on each side of the joint, they have in the 
former slipped out of place. In such a case the 
continuation of a stratum on the opposite side of 
a fault will be found to be depressed, perhaps a 
thousand feet or more. It will be seen at once 
how that, in sinking a new shaft into a coal-seam, 
the possibility of an unknown fault has to be 
brought into consideration, since the position of 
the seam may prove to have been depressed to 
such an extent as to cause it to be beyond work- 
able depth. Many seams, on the other hand, 
which would have remained altogether out of 
reach of mining operations, have been brought 
within workable depth by a series of step-faults, 
this being a term applied to a series of parallel 



GENERAL VIEW OF COAL-BEARING STRATA. 59 

faults, in none of which the amount of down- 
throw is great. 

The amount of the down-throw, or the slip- 
ping-down of the beds, is measured, vertically, 
from the point of disappearance of a layer to an 
imaginary continuation of the same layer from 
where it again appears beyond the fault. The 
plane of a fault is usually more or less inclined, 
the amount of the inclination being known as the 
hade of the fault, and it is a remarkable charac- 
teristic of faults that, as a general rule, they hade 
to the down-throw. This will be more clearly un- 
derstood when it is explained that, by its action, 
a seam of coal, which is subject to numerous 
faults, can never be pierced more than once by 
one and the same boring. In mountainous dis- 
tricts, however, there are occasions when the 
hade is to the up-throw, and this kind of fault is 
known as an inverted fault. 

Lines of faults extend sometimes for hundreds 
of miles. The great Pennine Fault of England 
is 130 miles long, and others extend for much 
greater distances. The surfaces on both sides of 
a fault are often smooth and highly polished by 
the movement which has taken place in the 
strata. They then show the phenomenon known 
as slicken-sides. Many faults have become filled 
with crystalline minerals in the form of veins of 
ore, deposited by infiltrating waters percolating 
through the natural fissures. 

In considering the formation and structure of 
the better-known coal-bearing beds of the car- 
boniferous age, we must not lose sight of the fact 
that important beds of coal also occur in strata 
of much more recent date. There are important 
coal-beds in India of Permian age. There are 



60 THE STORY OF A PIECE OF COAL, 

coal-beds of Liassic age in South Hungary and 
in Texas, and of Jurassic age in Virginia, as well 
as at Brora in Scotland ; there are large deposits 
of Cretaceous age in western North America; 
Cretaceous coal is also found in Moravia and 
Miocene Tertiary in Hungary. 

Again, older than the true carboniferous age, 
are the Silurian anthracites of Co. Cavan, and 
certain Norwegian coals, whilst in New South 
Wales we are confronted with an assemblage of 
coal-bearing strata which extend apparently from 
the Devonian into Mesozoic times. 

Still, the age we have considered more closely 
has an unrivalled right to the title, coal appear- 
ing there not merely as an occasional bed, but as 
a marked characteristic of the formation. 

The types of animal life which are found in 
this formation are varied, and although naturally 
enough they do not excel in number, there are 
yet sufficient varieties to show probabilities of 
the existence of many with which we are un- 
familiar. The highest forms yet found, show an 
advance as compared with those from earlier for- 
mations, and exhibit amphibian characteristics, 
intermediate between the two great classes of 
fishes and reptiles. Numerous specimens proper 
to the extinct order of labyrinthodontia have been 
arranged into at least a score of genera, these 
having been drawn from the coal-measures of 
Newcastle, Edinburgh, Kilkenny, Saarbruck, Ba- 
varia, Pennsylvania, and elsewhere. The Arche* 
gosaurus, which we have figured, and the Antkra- 
cosaurus, are forms which appear to have existed 
in great numbers in the swamps and lakes of the 
age. The fish of the period belong almost en- 
tirely to the ancient orders of the ganoids and 



GENERAL VIEW OF COAL-BEARING STRATA. 6 1 



placoids. Of the ganoids, the great megalichthys 
Hibberti ranges throughout the whole of the sys- 
tem. Wonderful ac- 
cumulations of fish 
remains are found 
at the base of the 
system, in the bone- 
bed of the Bristol 
coal-field, as well as 
in a similar bed 
at Armagh. Many 
fishes were armed 
with powerful coni- 
cal teeth, but the 
majority, like the 
existing Port Jack- 
son shark, were pos- 
sessed of massive 
palates, suited in 
some cases for 
crushing, and in 
others for cutting. 

In the mountain 
limestone we see, of 
course, the predom- 
inance of marine types, encrinital remains form- 
ing the greater proportion of the mass. There are 
occasional plant remains which bear evidence of 

having drifted for 
some distance from 
the shore. But 
next to the encri- 
nites, the corals 
are the most im- 
■ig. ^-Psammodusporosus. Pprtant and per- 

Crushing palate of a fish. SIStent. Corals OI 




FiG. 24. — Archegosaurus minor. 
Coal-measures. 




62 



THE STORY OF A PIECE OF COAL. 



most beautiful forms and capable of giving pol- 
ished marble-like sections, are in abundance. 
Polyzoa are well represented, of 
which the lace-coral {fenestella) 
and screw-coral (archimedopord) 
are instances. Cephalopoda are 
represented by the orthoceras, 
sometimes five or six feet long,, 
and goniatites, the forerunner of 
the familiar am??io?iite. Many 
species of brachiopods and la- 
mellibranchs are met with. Lin- 
gula, most persistent through- 
out all geological time, is abun- 
dant in the coal-shales, but not 
in the limestones. Aviculopecten 
is there abundant also. In the 
mountain limestone the last of 
Fig. 26.-Ort*oceras. * he trilobitCS (Phillipsia) is 
Mountain limestone, found. 




We have evi- 
dence of the ex- 
istence in the for- 
ests of a variety 
of centipede, speci- 
mens having 
been found in the 
erect stump of a 
hollow tree, al- 
though the fossil 
is an extremely 
rare one. The 
same may be said 
of the only two 
species of land- 




Fig. 27. — Fenestella i-etipora. 
Mountain limestone. 



GENERAL VIEW OF COAL-BEARING STRATA. 6$ 



snail which have been found connected with the 
coal-forests, viz., pupa vetusta and zonites priscus, 
both discov- 
ered in the 
cliffs of Nova 
Scotia. These 
are sufficient 
to demon- 
strate that the 

fauna of the period had already reached a high 
stage of development. In the estuaries of the 




Fig. 28. — Goniatites. Mountain limestone. 




Fig. 29. — Aviculopecten papyraceus. Coal-shale. 

day, masses of a species of freshwater mussel 
(anthracosid) were in existence, and these have 
left their remains in the shape of extensive beds 
of shells. They are familiar to the English miner 
as mussel-binds , and are as noticeable a feature 



64 THE STORY OF A PIECE OF COAL. 

of this long-ago period, as are the aggregations 
of mussels on every coast at the present day. 



CHAPTER III. 

VARIOUS FORMS OF COAL AND CARBON. 



In considering the various forms and combi 
nations into which coal enters, it is necessary that 
we should obtain a clear conception of what the 
substance called *' carbon " is, and its nature and 
properties generally, since this it is which forms 
such a large percentage of all kinds of coal, and 
which indeed forms the actual basis of it. In the 
shape of coke, of course, we have a fairly pure 
form of carbon, and this being produced, as we 
shall see presently, by the driving off of the vola- 
tile or vaporous constituents of coal, we are able 
to perceive by the residue how great a propor- 
tion of coal consists of carbon. In fact, the two 
have almost an identical meaning in the popular 
mind, and the fact that the great masses of 
strata, in which are contained our principal and 
most valuable seams of coal, are termed " car- 
boniferous," from the Latin carbo, coal, and fero y 
I bear, tends to perpetuate the existence of the 
idea. 

There is always a certain, though slight, quan- 
tity of carbon in the air, and this remains fairly 
constant in the open country. Small though it 
may be in proportion to the quantity of pure air 
in which it it found, it is yet sufficient to provide 
the carbon which is necessary to the growth of 
vegetable life. Just as some of the animals 






VARIOUS FORMS OF COAL AND CARBON. 65 

known popularly as the zoophytes, which are 
attached during life to rocks beneath the sea, 
are fed by means of currents of water which 
bring their food to them, so the leaves, which 
inhale carbon-food during the day through their 
under-surfaces, are provided with it by means of 
the currents of air which are always circulating 
around them; and while the fuel is being taken 
in beneath, the heat and light are being received 
from above, and the sun supplies the motive 
power to digestion. 

It is assumed that it is within the knowledge 
of all that, for the origin of the various seams 
and beds of coaly combinations which exist in the 
earth's crust, we must look to the vegetable world. 
If, however, we could go so far back in the world's 
history as the period when our incandescent orb 
had only just severed connection with a gradu- 
ally diminishing sun, we should probably find the 
carbon there, but locked up in the bonds of 
chemical affinities with other elements, and exist- 
ing therewith in a gaseous condition. But, as 
the solidifying process went on and as the vege- 
table world afterwards made its appearance, the 
carbon became, so to speak, wrenched from its 
combinations, and being absorbed by trees and 
plants, finally became deposited amongst the ruins 
of a former vegetable world, and is now presented 
to us in the form of coal. 

We are able to trace the gradual changes 
through which the pasty mass of decaying vege- 
tation passed, in consequence of the fact that we 
have this material locked up in various stages of 
carbonisation, in the strata beneath our feet. 
These we propose to deal with individually, in as 
unscientific and untechnical a manner as possible. 



66 THE STORY OF A PIECE OF COAL. 

First of all, when a mass of vegetable matter 
commences to decay, it soon loses its colour. 
There is no more noticeable proof of this, than 
that when vitality is withdrawn from the leaves 
of autumn, they at once commence to assume a 
rusty or an ashen colour. Let the leaves but fall 
to the ground, and be exposed to the early frosts 
of October, the damp mists and rains of No- 
vember, and the rapid change of colour is at 
once apparent. Trodden under foot they soon 
assume a dirty blackish hue, and even when 
removed they leave a carbonaceous trace of 
themselves behind them, where they had rested. 
Another proof of the rapid acquisition of their 
coaly hue is noticeable in the spring of the year. 
When the trees have burst forth and the buds 
are rapidly opening, the cases in which the buds 
of such trees as the horse-chestnut have been 
enclosed will be found cast off, and strewing the 
path beneath. Moistened by the rains and the 
damp night-mists, and trodden under foot, these 
cases assume a jet black hue, and are to all appear- 
ance like coal in the very first stages of formation. 

But of course coal is not made up wholly and 
only of leaves. The branches of trees, twigs of 
all sizes, and sometimes whole trunks of trees 
are found, the last often remaining in their up- 
right position, and piercing the strata which have 
been formed above them. At other times they 
lie horizontally on the bed of coal, having been 
thrown down previously to the formation of the 
shale or sandstone, which now rests upon them. 
They are often petrified into solid sandstone 
themselves, whilst leaving a rind of coal where 
formerly was the bark. Although the trunk of 
a tree looks so very different to the leaves 



VARIOUS FORMS OF COAL AND CARBON. 67 

which it bears upon its branches, it is only natu- 
rally to be supposed that, as they are both built 
up after the same manner from the juices of the 
earth and the nourishment in the atmosphere, 
they would have a similar chemical composi- 
tion. One very palpable proof of the carbonace- 
ous character of tree-trunks suggests itself. Take 
in your hand a few dead twigs or sticks from which 
the leaves have long since dropped ; pull away 
the dead parts of the ivy which has been creep- 
ing over the summer-house ; or clasp a gnarled 
old monster of the forest in your arms, and you 
will quickly find your hand covered with a black 
smut, which is nothing but the result of the first 
stage which the living plant has made, in its prog- 
ress towards its condition as dead coal. But 
an easy, though rough, chemical proof of the 
constituents of wood, can be made by placing a 
few pieces of wood in a medium-sized test-tube, 
and holding it over a flame. In a short time a 
certain quantity of steam will be driven off, next 
the gaseous constituents of wood, and finally 
nothing will be left but a few pieces of black 
brittle charcoal. The process is of course the 
same in a fire-grate, only that here more com- 
plete combustion of the wood takes place owing 
to its being immediately exposed to the action of 
the flames. If we adopt the same experiment 
with some pieces of coal, the action is similar, only 
that in this case the quantity of gases given off is 
not so great, coal containing a greater proportion 
of carbon than wood, owing to the fact that, dur- 
ing its long burial in the bowels of the earth, it 
has been acted upon in such a way as to lose a 
great part of its volatile constituents. 

From processes, therefore, which are to be 



68 THE STORY OF A PIECE OF COAL. 

seen going on around us, it is easily possible to 
satisfy ourselves that vegetation will in the long 
run undergo such changes as will result in the 
formation of coal. 

There are certain parts in most countries, and 
particularly in Ireland, where masses of vegetation 
have undergone a still further change in meta- 
morphism, namely, in the well-known and famous 
peat-bogs. Ireland is par excellence the land of 
bogs, some three millions of acres being said to 
be covered by them, and they yield an almost 
inexhaustible supply of peat. One of the peat- 
bogs near the Shannon is between two and three 
miles in breadth and no less than fifty in length, 
whilst its depth varies from 13 feet to as much 
as 47 feet. Peat-bogs have in no way ceased to be 
formed, for at their surfaces the peat-moss grows 
afresh every year ; and rushes, horse-tails, and 
reeds of all descriptions grow and thrive each 
year upon the ruins of their ancestors. The for- 
mation of such accumulations of decaying vege- 
tation would only be possible where the physical 
conditions of the country allowed of an abundant 
rainfall, and depressions in the surface of the 
land to retain the moisture. Where extensive 
deforesting operations have taken place, peat-bogs 
have often been formed, and many of those in 
existence in Europe undoubtedly owe their forma- 
tion to that destruction of forests which went on 
under the sway of the Romans. Natural drainage 
would soon be obstructed by fallen trees, and the 
formation of marsh-land would follow; then with 
the growth of marsh-plants and their successive 
annual decay, a peaty mass would collect, which 
would quickly grow in thickness without let or 
hindrance. 






VARIOUS FORMS OF COAL AND CARBON. 69 

In considering the existence of inland peat- 
bogs, we must not lose sight of the fact that there 
are subterranean forest-beds on various parts of 
our coasts, which also rest upon their own beds 
of peaty matter, and very possibly when in the 
future they are covered up by marine deposits, 
they will have fairly started on their way towards 
becoming coal. 

Peat-bogs do not wholly consist of peat, and 
nothing else. The trunks of such trees as the 
oak, yew, and fir, are often found mingled with 
the remains of mosses and reeds, and these often 
assume a decidedly coaly aspect. From the 
famous Bog of Allen in Ireland, pieces of oak, 
generally known as " bog-oak," which have been 
buried for generations in peat, have been ex- 
cavated. These are as black as any 4 coal can 
well be, and are sufficiently hard to allow of their 
being used in the manufacture of brooches and 
other ornamental objects. Another use to which 
peat of some kinds has been put is in the manu- 
facture of yarn, the result being a material which 
is said to resemble brown worsted. On digging 
a ditch to drain a part of a swamp in Maine, 
in which peat to a depth of twenty feet had ac- 
cumulated, a substance similar to cannel coal 
itself was found. As we shall see presently, 
cannel coal is one of the earliest stages of true 
coal, and the discovery proved that under certain 
conditions as to heat and pressure, which in this 
case happened to be present, the materials which 
form peat may also be metamorphosed into true 
coal. 

Darwin, in his well-known " Voyage in the 
Beagle" gives a peculiarly interesting description 
of the condition of the peat-beds in the Chonos 



JO THE STORY OF A PIECE OF COAL. 

Archipelago, off the Chilian coast, and of their 
mode of formation. " In these islands/' he says, 
" cryptogamic plants find a most congenial 
climate, and within the forest the number of 
species and great abundance of mosses, lichens, 
and small ferns, is quite extraordinary. In Tierra 
del Fuego every level piece of land is invariably 
covered by a thick bed of peat. In the Chonos 
Archipelago where the nature of the climate more 
closely approaches that of Tierra del Fuego, every 
patch of level ground is covered by two species 
of plants {Astelia pumila and Donatia megellanica), 
which by their joint decay compose a thick bed 
of elastic peat. 

" In Tierra del Fuego, above the region of 
woodland, the former of these eminently sociable 
plants is the chief agent in the production of peat. 
Fresh leaves are always succeeding one to the 
other round the central tap-root ; the lower ones 
soon decay, and in tracing a root downwards in 
the peat, the leaves, yet holding their places, can 
be observed passing through every stage of de- 
composition, till the whole becomes blended in 
one confused mass. The Astelia is assisted by a 
few other plants, — here and there *a small creep- 
ing Myrtus (Af. nummu/aria), with a woody stem 
like our cranberry and with a sweet berry, — an 
Empetrum (£. rubrum), like our heath, — a rush 
(Juncus grandiflorus), are nearly the only ones 
that grow on the swampy surface. These plants, 
though possessing a very close general resem- 
blance to the English species of the same genera, 
are different. In the more level parts of the 
country the surface of the peat is broken up into 
little pools of water, which stand at different 
heights, and appear as if artificially excavated. 



VARIOUS FORMS OF COAL AND CARBON. 71 

Small streams of water, flowing underground,, 
complete the disorganisation of the vegetable 
matter, and consolidate the whole. 

" The climate of the southern part of America 
appears particularly favourable to the production 
of peat. In the Falkland Islands almost every 
kind of plant, even the coarse grass which covers 
the whole surface of the land, becomes converted 
into this substance : scarcely any situation checks 
its growth ; some of the beds are as much as 
twelve feet thick, and the lower part becomes so 
solid when dry that it will hardly burn. Although 
every plant lends its aid, yet in most parts the 
Astelia is the most efficient. 

" It is rather a singular circumstance, as being 
so very different from what occurs in Europe,, 
that I nowhere saw moss forming by its decay 
any portion of the peat in South America. With 
respect to the northern limit at which the climate 
allows of that peculiar kind of slow decomposition 
which is necessary for its production, I believe 
that in Chiloe (lat. 41 to 42 ), although there is 
much swampy ground, no well characterised peat 
occurs; but in the Chonos Islands, three degrees 
farther southward, we have seen that it is abun- 
dant. On the eastern coast in La Plata (lat. 35 ) 
I was told by a Spanish resident, who had visited 
Ireland, that he had often sought for this sub- 
stance, but had never been able to find any. He 
showed me, as the nearest approach to it which 
he had discovered, a black peaty soil, so pene- 
trated with roots as to allow of an extremely slow 
and imperfect combustion/' 

The next stage in the making of coal is one in 
which the change has proceeded a long way from 
the starting-point. Lignite is the name which 



- 



72 THE STORY OF A PIECE OF COAL. 

has been applied to a form of impure coal, which 
sometimes goes under the name of " brown coal.' 1 
It is not a true coal, and is a very long way from 
that final stage to which it must attain ere it takes 
rank with the most valuable of earth's products. 
From the very commencement, an action has 
been going on which has caused the amount of 
the gaseous constituents to become less and less, 
and which has consequently caused the carbon 
remaining behind to occupy an increasingly large 
proportion of the whole mass. So, when we 
arrive at the lignite stage, we find that a consid- 
erable quantity of volatile matter has already 
been parted with, and that the carbon, which in 
ordinary living wood is about 50 per cent, of the 
whole, has already increased to about 67 per cent. 
In most lignites there is, as a rule, a comparatively 
large proportion of sulphur, and in such cases it 
is rendered useless as a domestic fuel. It has 
been used as a fuel in various processes of manu- 
facture, and the lignite of the well-known Bovey 
Tracey beds has been utilised in this way at the 
neighbouring potteries. As compared with true 
coal, it is distinguished by the abundance of 
smoke which it produces and the choking sul- 
phurous fumes which also accompany its combus- 
tion, but it is largely used in Germany asa useful 
source of paraffin and illuminating oils. In 
Silesia, Saxony, and in the district about Bonn, 
large quantities of lignite are mined, and used as 
fuel. Large stores of lignite are known to exist 
in the Weald of the south-east of England, and 
although the mining operations which were car- 
ried on at one time at Heathfield, Bexhill, and 
other places, were failures so far as the actual 
discovery of true coal was concerned, yet there 



VARIOUS FORMS OF COAL AND CARBON. 73 

can be no doubt as to the future value of the 
lignite in these parts, when England's supplies of 
coal approach exhaustion, and attention is turned 
to other directions for the future source of her 
gas and paraffin oils. 

The tertiary coals of America, found in Nevada, 
Oregon, and the Saskatchewan region, and even 
some of those of cretaceous age, are classed as lig- 
nite. The more perfect coals are, however, so 
abundant and accessible in the United States 
that lignite is mined and used only in localities 
remote from the anthracite and bituminous fields. 

We have now closely approached to true coal, 
and the next step which we shall take will be to 
consider the varieties in which the black mineral 
itself is found. The principal of these varieties 
are as follows, against each being placed the 
average proportion of pure carbon which it con- 
tains : — 

Cannel, Candle, or Parrott Coal, 84 per cent. ; 

Bituminous, or Soft Coal, 88 per cent., shading 
through Semi-Bituminous and Semi-Anthra- 
cite to 

Anthracite, Blind Coal, Culm, Glance, or Stone 
Coal, 93 per cent. 

As far as the gas-making properties of the first 
two are concerned, the relative proportions of 
carbon and volatile products are much the same. 
Everybody knows a piece of cannel coal when it 
is seen, how it appears almost to have been once 
in a molten condition, and how it breaks with a 
conchoidal fracture, as opposed to the cleavage 
of bituminous coal into thin layers; and, most 
apparent and most noticeable of all, how T it does 
not soil the hands after the manner of ordinary 
coal. It is at times so dense and compact that 



74 THE STORY OF A PIECE OF COAL. 

it has been fashioned into ornaments, and is ca- 
pable of receiving a polish like jet. From the 
large percentage of volatile products which it 
contains, it is greatly used in English gasworks. 
% The highly bituminous, " fat," or "caking" 
coals when heated become plastic and give off 
much gas. If the mass is not allowed to burn 
a porous product is left which is known as coke. 
In the iron regions the gas is burnt off from great 
quantities of this coal in kilns, so as to obtain the 
coke for the iron furnaces. The same kind of 
coal is also brought into cities where the gas is 
carefully distilled off and collected while the coke 
is disposed of as a bye-product. The grades be- 
tween caking coal and anthracite are especially 
valuable for the rapid production of steam, as 
is required in locomotives, and hence are often 
called " steam " coals. These more or less bi- 
tuminous varieties are commonly used in Eng- 
land and the central parts of the United States 
for domestic purposes. North and east of Penn- 
sylvania anthracite is the domestic coal. The 
more coal approaches the character of anthracite 
the more difficult it is to get it to burn, but 
when at last fairly alight it gives out great heat, 
and what is more important, a less quantity of 
gas, smoke, ammonia, sulphurous fumes, and ash. 
It is thus an admirable fuel for household pur- 
poses, and with hot blast it may be used in iron- 
smelting furnaces. In the Eastern States soft 
coal is familiar only in the blacksmith's forge. 
% It is a significant fact and one which proves 
that the various kinds of coal which are found 
are nothing but stages begotten by different de- 
grees of disentanglement of the contained gases, 
that where, as in some parts, a mass of basalt has 



VARIOUS FORMS OF COAL AND CARBON. 75 

come into contact with ordinary bituminous coal, 
the coal has assumed the character of anthracite, 
whilst the change has in some instances gone so> 
far as to convert the anthracite into graphite. 
The basalt, which is one of the igneous rocks, 
has been erupted into the coal-seam in a state 
of fusion, and the heat contained in it has been 
sufficient to cause the disentanglement of the; 
gases, the extraction of which from the coal 
brings about the condition of anthracite and 
graphite. 

\/ The mention of graphite brings us to the next 
stage. Graphite, plumbago, or, as it is more 
commonly called, black lead, which we may say 
in passing, has nothing of lead about it at all, is 
best known in the shape of that very useful and 
cosmopolitan article, the black-lead pencil. This 
is even purer carbon than anthracite, not more 
than 5 per cent, of ash and other impurities being 
present. It is well known by its grey metallic 
lustre; the chemist uses it mixed with fire-clay 
to make his crucibles; the engineer uses it, finely 
powdered, to lubricate his machinery ; the house- 
keeper uses it to " blacklead " her stoves to pre- 
vent them from rusting. An imperfect graphite 
is found inside some of the hottest retorts from 
which gas is distilled, and this is used as the nega- 
tive element in zinc and carbon electricity-making 
cells, whilst its use as the electrodes or carbons 
of the arc-lamp is becoming more and more widely 
adopted, as installations of electric light become 
more general. 

•^ Over a million pounds of graphite are mined 
yearly at Ticonderoga, N. Y., and a small quantity 
is obtained in Berks County, Pa. This output 
supplies only about 5 per cent, of the domestic 



J 6 THE STORY OF A PIECE OF COAL. 

demand. Germany produces a considerable quan- 
tity of this mineral, but the bulk of the world's 
supply comes from Ceylon. Extensive deposits 
of graphite are found in rocks of the Laurentian 
age in Canada. In this formation nothing which 
can undoubtedly be classed as organic has yet 
been discovered. Life at this early period must 
have found its home in low and humble forms and 
if the eozoon of Dawson, which has been thought 
to represent the earliest types of life, turns out 
after all not to be organic, but only a deceptive 
appearance assumed by certain of the strata, we 
at least know that it must have been in similarly 
humble forms that life, if it existed at all, did 
then exist. We can scarcely, therefore, expect 
that the vegetable world had made any great 
advance in complexity of organism at this time, 
otherwise the supplies of graphite or plumbago 
which are found in the formation, would be 
attributed to dense forest growths, acted upon, 
after death, in a similar manner to that which 
awaited the vegetation which, ages after, went 
to form beds of coal. At present we know of 
no source of carbon except through the interven- 
tion and the chemical action of plants. Like 
iron, carbon is seldom found on the earth except 
in combination. If there were no growth of 
vegetation at this far-away period to give rise 
to these deposits of graphite, we are compelled 
to ask ourselves whether, perchance, there did not 
then exist conditions of which we are not now 
cognisant on the earth, and which allowed 
graphite to be formed without assistance from 
the vegetable kingdom. At present, however, 
science is in the dark as to any other process of 
its formation, and we are left to assume that the 






VARIOUS FORMS OF COAL AND CARBON. 77 



vegetable growth of the time was enormous in 
quantity, although there is nothing- to show the 
kind of vegetation, whether humble mosses or 
tall forest trees, which went to constitute the 
masses of graphite. Geologists will agree that 
this is no small assumption to make, since, if 
true, it may show that there was an abundance 
of vegetation at a time when animal life was 
hidden in one or more very obscure forms, one 
only of which has so far been detected, and 
whose very identity is strongly doubted by nearly 
all competent judges. At the same time there may 
have been an abundance of both animal and vege- 
table life at the time. We must not forget that 
it is a well-ascertained fact that 
in later ages, the minute seed- 
spores of forest trees were in 
such abundance as to form im- 
portant seams of coal in the 
true carboniferous era, the trees 
which gave birth to them being 
now classed amongst the hum- 
ble cryptogams, the ferns, and 
club-mosses, &c. The graphite 
of Laurentian age may not im- 
probably have been caused by 
deposits of minute portions of Y ig. 3 o.-Lepzdoden- 
similar lowly specimens of vege- dron. Portion of 
table life, and if the eozoon, the 
" dawn-animalcule," does repre- 
sent the animal life of the time, 
life whose types were too minute 
to leave undoubted traces of their existence, both 
animal life and vegetable life maybe looked upon 
as existing side by side in extremely humble 
forms, neither as yet having taken an undoubted 




Sandstone stem af- 
ter removal of bark 
of a giant club- 
moss. 



78 THE STORY OF A PIECE OF COAL. 

step forward in advance of the other in respect 
to complexity of organism. 

There is but one more form of carbon with 
which we have to deal in running through the 
series. We have seen that coal is not the sum- 
mum bonum of the series. Other transformations 
take place after the stage of coal is reached, 
which, by the continued disentanglement of gases, 
finally bring about the plumbago stage. 

What the action is which transforms plumbago 
or some other form of carbon into the condition 
of a diamond cannot be stated. Diamond is the 
purest form of carbon found in nature. It is a 
beautiful object, alike from the results of its 
powers of refraction, as also from the form into 
which its carbon has been crystallised. How 
Nature, in her wonderful laboratory, has precipi- 
tated the diamond, with its wonderful powers of 
spectrum analysis, we cannot say with certainty. 
Certain chemists have, at a great expense, pro- 
duced crystals, which, in every respect, stand 
the tests of true diamonds; but the process of 
their production at a great expense has in no 
way diminished the value of the natural pro- 
duct. 

The process by which artificial diamonds have 
been produced is so interesting, and the subject 
may prove to be of so great importance, that a 
few remarks upon the process may not be unac- 
ceptable. 

The experiments of the great French chemist, 
Dumas, and others, satisfactorily proved the fact, 
which has ever since been considered thoroughly 
established, that the diamond is nothing but car- 
bon crystallised in nearly a pure state, and many 
chemists have since been engaged in the hitherto 



VARIOUS FORMS OF COAL AND CARBON. 79 

futile endeavour to turn ordinary carbon into the 
true diamond. 

Despretz at one time considered that he had 
discovered the process, which consisted in his case 
of submitting a piece of charcoal to the action of 
an electric battery, having in his mind the similar 
process of electrolysis, by which water is divided 
up into the two gases, hydrogen and oxygen. He 
obtained a microscopic deposit on the poles of 
the battery, which he pronounced to be diamond 
dust, but which, a long time after, was proved to 
be nothing but graphite in a crystallised state. 
This was, however, certainly a step in the right 
direction. 

The honour of first accomplishing the task 
fell to Mr. Hannay, of Glasgow, who succeeded 
in producing very small but comparatively soft 
diamonds, by heating lampblack under great 
pressure, in company with one or two other in- 
gredients. The process was a costly one, and 
beyond being a great scientific feat, the discovery 
led to little result. 

A young French chemist, M. Henri Moissan, 
has since come to the front, and the diamonds 
which he has produced have stood every test for 
the true diamond to which they could be subjected ; 
above all, the density of the product is 3.5, /. e. y 
that of the diamond, that of graphite reaching 2 
only. 

He recognised that in all diamonds which he 
had consumed — and he consumed some ^150 
worth in order to assure himself of the fact — - 
there were always traces of iron in their composi- 
tion. He saw that iron in fusion, like other 
metals, always dissolves a certain quantity of car- 
bon. Might it not be that molten iron, cooling 



80 THE STORY OF A PIECE OF COAL. 

in the presence of carbon, deep in volcanic depths 
where there was little scope for the iron to ex- 
pand in assuming the solid form, would exert 
such tremendous pressure upon the particles of 
carbon which it absorbed, that these would assume 
the crystalline state ? 

He packed a cylinder of soft iron with the 
carbon of sugar, and placed the whole in a cruci- 
ble filled with molten iron, which was raised to a 
temperature of 3000 by means of an electric fur- 
nace. The soft cylinder melted, and dissolved 
a large portion of the carbon. The crucible was 
thrown into water, and a mass of solid iron was 
formed. It was allowed further to cool in the 
open air, but the expansion which the iron would 
have undergone on cooling, was checked by the 
crucible which contained it. The result was a 
tremendous pressure, during which the carbon, 
which was still dissolved, was crystallised into 
minute diamonds. 

These showed themselves as minute points 
which were easily separable from the mass by the 
action of acids. Thus the wonderful transforma- 
tion from sugar to the diamond was accomplished. 

It should be mentioned that iron is one of the 
few substances that possess the peculiar property 
of expanding when passing from the liquid to the 
solid state. 

The diamonds so obtained were of both kinds. 
The particles of white diamond resembled in 
every respect the true brilliant. But there was 
also an appreciable quantity of the variety known 
as the " black diamond." These diamonds seem 
to approximate more closely to carbon as we are 
most familiar with it. They are not considered 
as of such value as the transparent form, but 



VARIOUS FORMS OF COAL AND CARBON. 8l 

they are still of considerable commercial value. 
The carbonado, as this kind is called, possesses so 
great a degree of hardness that by means of it it 
is possible to bore through the hardest rocks. 
The diamond drill, used for boring purposes, is 
furnished around the outer edge of the cylinder 
of the " boring bit," as it is called, with perhaps 
a dozen black diamonds, together with another 
row of Brazilian diamonds on the inside. By the 
rotation of the boring tool the sharp edges of the 
diamonds cut their way through rocks of all de- 
grees of hardness, leaving a core of the rock cut 
through, in the centre of the cylindrical drill. It 
is found that the durability of the natural edge of 
the diamond is far greater than that of the edge 
caused by artificial cutting and trimming. The 
cutting of a pane of glass by means of a ring set 
with an artificially cut diamond, cannot therefore 
be done without injuring to a slight extent the 
edge of the stone. 

The diamond is the hardest of all known 
substances, leaving a scratch on any substance 
across which it may be drawn. Yet it is one 
whose form can be changed, and whose hardness 
can be completely destroyed, by the simple process 
of combustion. It can be deprived of its high 
lustre, and of its power of breaking up by refrac- 
tion the light of the sun into the various tints of 
the solar spectrum, simply by heating it to a red 
heat, and then plunging it into a jar of oxygen 
gas. It immediately expands, changes into a 
coky mass, and burns away. The product left 
behind is a mixture of carbon and oxygen, in the 
proportions in which it is met with in carbonic- 
anhydride, or, carbonic acid gas deprived of its 
water. This is indeed a strange transformation, 
6 



$2 THE STORY OF A PIECE OF COAL. 

from the most valuable of all our precious stones 
to a compound which is the same in chemical con- 
stituents as the poisonous gas which we and all 
animals exhale. But there is this to be said. 
Probably in the far-away days when the diamond 
began to be formed, the tree or other vegetable 
product which was its far-removed ancestor ab- 
stracted carbonic acid gas from the atmosphere, 
just as do our plants in the present day. By this 
means it obtained the carbon wherewith to build 
up its tissues. Thus the combustion of the dia- 
mond into carbonic-anhydride now is, after all, 
only a return to the same compound out of which 
it was originally formed. How it was formed is 
a secret ; probably the time occupied in the for- 
mation of the diamond may be counted by centu- 
ries, but the time of its re-transformation into a 
mass of coky matter is but the work of seconds ! 

There is another form of carbon which was 
formerly of much greater importance than it is 
now, and which, although not a natural product, 
is yet deserving of some notice here. Charcoal 
is the substance referred to. 

In early days the word " coal," or, as it was 
also spelt, " cole," was applied to any substance 
which was used as fuel ; hence we have a refer- 
ence in the Bible to a " fire of coals," "so trans- 
lated when the meaning to be conveyed was prob- 
ably not coal as we know it. Wood was formerly 
known as coal, whilst charred wood received the 
name of charred coal, which was soon corrupted 
into charcoal. The charcoal-burners of years 
gone by were a far more flourishing community 
than they are now. When the old baronial halls 
and country-seats depended on them for the basis 
of their fuel, and the log was a more frequent 






VARIOUS FORMS OF COAL AND CARBON. 83 

occupant of the fire-grate than now, these occu- 
piers of midforest were a people of some impor- 
tance. 

We must not overlook the fact that there is 
another form of charcoal, namely, animal char- 
coal or bone-black. This can be obtained by 
heating bones to redness in closed iron vessels. 
In the refining of raw sugar the decoloration of 
the syrup is brought about by filtering it through 
animal-charcoal ; by this means the syrup is ren- 
dered colourless. 

When properly prepared, charcoal exhibits 
very distinctly the rings of annual growth which 
may have characterised the wood from which it 
was formed. It is very light in consequence of 
its porous nature, and it is wonderfully indestruc- 
tible. 

But its greatest, because it is its most useful 
property, is undoubtedly the power which it has 
of absorbing great quantities of gas into itself. 
It is in fact what may be termed an all-round 
purifier. It is a deodoriser, a disinfectant, and a 
decoloriser. It is an absorbent of bad odours, 
and partially removes the smell from tainted 
meat. It has been used when offensive manures 
have been spread over soils, with the same object 
in view, and its use for the purification of water 
is well known to all users of filters. Some idea 
of its power as a disinfectant may be gained by 
the fact that one volume of wood-charcoal will 
absorb no less than 90 volumes of ammonia, 35 
volumes of carbonic anhydride, and 65 volumes 
of sulphurous anhydride. 

Other forms of carbon which are well-known 
are (1) coke, the residue left when coal has been 
subjected to a great heat in a closed retort ; (2) 



84 THE STORY OF A PIECE OF COAL. 

soot and lamp-black, the former of which is use- 
ful as a manure in consequence of ammonia being 
present in it, whilst the latter is a specially pre- 
pared soot, and is used chiefly as the colouring 
matter of black paint and as the basis of Indian 
ink and printers' ink. 



CHAPTER IV. 

THE COAL-MINE AND ITS DANGERS. 

It is somewhat strange to think that where 
once existed the solitudes of an ancient carbon- 
iferous forest now is the site of a busy under- 
ground town. For a town it really is. The vari- 
ous roads and passages which are cut through the 
solid coal as excavation of a coal-mine proceeds, 
represent to a stranger all the intricacies of a 
well-planned town. Nor is the extent of these 
underground towns a thing to be despised. There 
is an old pit near Newcastle which contains not 
less than fifty miles of passages. Other pits 
there are whose main thoroughfares in a direct 
line are not less than four or five miles in length, 
and this, it must be borne in mind, is the result of 
excavation wrought by human hands and human 
labour. 

So great an extent of passages necessarily re- 
quires some special means of keeping the air 
within it in a pure state, such as will render it fit 
for the workers to breathe. The further one 
would go from the main thorougfare in such a 
mine, the less likely one would be to find air of 
sufficient purity for the purpose. It is as a con- 



THE COAL-MINE AND ITS DANGERS. 



85 



sequence necessary to take some special steps to* 
provide an efficient system of ventilation through- 




Fig. 31.— Engine-House and Buildings at head of a Coal-Pit. 

out the mine. This is effectually done by two« 
shafts, called respectively the downcast and the 
upcast shaft. A shaft is in reality a very deep 
well, and may be circular, rectangular or oval in 
form. In order to keep out water which may be 
struck in passing through the various strata, it is 
protected by plank or wood tubbing, or the shaft 
is bricked over, or sometimes even cast-iron seg- 
ments are sunk. In many shafts which, owing to 
their great depth, pass through strata of every 
degree of looseness or viscosity? all three methods 
are utilised in turn. In Westphalia, where coal is 
worked beneath strata of more recent geological 
age, narrow shafts have been, in many cases, 
sunk by means of boring apparatus, in preference 
to the usual process of excavation, and the prac- 
tice has since been adopted in South Wales. In 
England the usual form of the pit is circular, but 
elliptical and rectangular pits are also in use. On 
the Continent polygonal-shaped shafts are not 



S6 THE STORY OF A PIECE OF COAL. 

uncommon, while in America they are usually 
rectangular, measuring about twelve by thirty 
feet, and divided into a pump-way, two carriage- 
ways, and an air-way. 

If there be one of these shafts at one end of 
the mine, and another at a remote distance from 
it, a movement of the air will at once begin, and 
a rough kind of ventilation will ensue. This is, 
however, quite insufficient to provide the neces- 
sary quantity of air for inhalation by the army 
of workers in the coal-mine, for the current thus 
set up does not even provide sufficient force to 
remove the effete air and impurities which ac- 
cumulate from hundreds of perspiring human 
bodies. 

It is therefore necessary to introduce some 
artificial means, by which a strong and regular 
current shall pass down one shaft, through the 
mine in all its workings, and out at the other 
shaft. This is accomplished in various ways. It 
took many years before those interested in mines 
came thoroughly to understand how properly to 
secure ventilation, and in bygone days the system 
was so thoroughly bad that a tremendous amount 
of sickness prevailed amongst the miners, owing 
to the poisonous effects of breathing the same air 
over and over again, charged, as it was, with 
more or less of the gases given off by the coal 
itself. Now, those miners who do so great a part 
in furnishing the means of warming our houses in 
winter, have the best contrivances which can be 
devised to furnish them with an everflowing cur- 
rent of fresh air. 

^ Amongst the various mechanical appliances 
which have been used to ensure ventilation may 
be mentioned pumps, fans, and pneumatic screws. 



THE COAL-MINE AND ITS DANGERS. 87 

There is, as we have said, a certain, though slight, 
movement of the air in the two columns which 
constitute the upcast and the downcast shafts, 
but in order that a current may flow which shall 
be equal to the necessities of the miners, some 
means are necessary by which this condition of 
almost equilibrium shall be considerably dis- 
turbed, and a current created which shall sweep 
all foul gases before it. One plan was to force 
fresh air into the downcast, which should in a 
sense push the foetid air away by the upcast, and 
so draw the gases in the train of the exhausted 
air. In other cases the plan was adopted of pro- 
viding a continual falling of water down the down- 
cast shaft. 

These various plans have almost all given 
way to that which is the most serviceable of all, 
namely, the plan of having an immense furnace 
constantly burning in a specially-constructed 
chamber at the bottom of the upcast. By this 
means the column of air above it becomes rarefied 
under the heat, and ascends, whilst the cooler air 
from the downcast rushes in and spreads itself in 
all directions whence the bad air has already been 
drawn. On the other hand, to so great a state of 
perfection have ventilating fans been brought, 
that one was recently erected which would be 
capable of changing the air of Westminster Hall 
thirty times in one hour. 

Having procured a current of sufficient power, 
it will be at once understood that, if left to its 
own will, it would take the nearest path which 
might lie between its entrance and its exit, and, 
in this way, ventilating the principal street only, 
would leave all the many off-shoots from it undis- 
turbed. It is consequently manipulated by means 



SS THE STORY OF A PIECE OF COAL. 

of barriers and tight-fitting doors, in such a way 
that the current is bound in turn to traverse every 
portion of the mine. A large number of boys, 
known as trappers, are employed in opening the 
doors to all comers, and in carefully closing the 
doors immediately after they have passed, in 
order that the current may not circulate through 
passages along which it is not intended that it 
Should pass. 

The greatest dangers which await the miners 
are those which result, in the form of terrible ex- 
plosions, from the presence of inflammable gases 
in the mines. The great walls of coal which 
bound the passages in mines are constantly ex- 
uding supplies of gas into the air. When a bank 
of coal is brought down by an artificial explosion, 
by dynamite, by lime cartridges, or by some 
other agency, large quantities of gas are some- 
times disengaged, and not only is this highly det- 
rimental to the health of the miners, if not car- 
ried away by proper ventilation, but it constitutes 
a constant danger which may at any time cause 
an explosion when a naked light is brought into 
contact with it. Fire-damp may be sometimes 
heard issuing from fiery seams with a peculiar 
hissing sound. If the volume be great, the gas 
forms what is called a blower, and this often hap- 
pens in the neighbourhood of a fault. When coal 
is brought down in any large volume, the blow T ers 
which commence may be exhausted in a few mo- 
ments. Others, however, have been known to 
last for years, this being the case at Wallsend, 
w r here the blower gave off 120 feet of gas per 
minute. In such cases the gas is usually con- 
veyed in pipes to a place where it can be burned 
in safety. 



THE COAL-MINE AND ITS DANGERS. 89 

In the early days of coal-mining the ex- 
plosions caused by this gas soon received the 
serious attention of the scientific men of the age. 
In the Philosophical Transactions of the Royal 
Society we find a record of a gas explosion in 1677. 
The amusing part of such records was that the 
explosions were ascribed by the miners to sup- 
ernatural agencies. Little attention seemed to 
have been paid to the fact, which has since so 
thoroughly been established, that the explosions 
were caused by accumulations of gas, mixed in 
certain proportions with air. As a consequence, 
tallow candles with an exposed flame were freely 
used, especially in Britain. These were placed in 
niches in the workings, where they would give to 
the pitman the greatest amount of light. Previ- 
ous to the introduction of the safety-lamp, work- 
ings were tested before the men entered them, by 
" trying the candle. " Owing to the specific 
gravity of fire-damp (.555) being less than that of 
air, it always finds a lodgment at the roofs ot 
the workings, so that, to test the condition of the 
air, it was necessary to steadily raise the candle 
to the roof at certain places in the passages, and 
watch carefully the action of the flame. The 
presence of fire-damp would be shown by the 
flame assuming a blue colour, and by its elonga- 
tion ; the presence of other gases could be de- 
tected by an experienced man by certain pecul- 
iarities in the tint of the flame. This testing 
with the open flame has almost entirely ceased 
since the introduction of the perfected Davy lamp. 

The use of candles for illumination soon gave 
place in most of the large collieries to the intro- 
duction of small oil-lamps. In the less fiery 
mines on the Continent, oil-lamps of the well- 



90 THE STORY OF A PIECE OF COAL. 

known Etruscan pattern are still in use, whilst 
small metal lamps, which can conveniently be 
attached to the cap of the worker, are the kind 
commonly used in the United States. These 
lamps are very useful in getting the coal from 
the thinner seams, where progress has to be 
made on the hands and feet. At the close of 
the last century, as workings began to be carried 
deeper, and coal was obtained from places more 
and more infested with fire-damp, it soon came 
to be realised that the old methods of illumina- 
tion would have to be replaced by others of a 
safer nature. 

It is noteworthy that mere red heat is insuffi- 
cient in itself to ignite fire-damp, actual contact 
with flame being necessary for this purpose. 
Bearing this in mind, Spedding, the discoverer of 
the fact, invented what is known as the " steel- 
mill " for illuminating purposes. In this a toothed 
wheel was made to play upon a piece of steel, 
the sparks thus caused being sufficient to give a 
moderate amount of illumination. It is found, 
however, that this method was not always trust- 
worthy, and lamps were introduced by Humboldt 
in 1796, and by Clanny in 1806. In these lamps 
the air which fed the flame was isolated .from the 
air of the mine by having to bubble through a 
liquid. Many miners were not, however, pro- 
vided with these lamps, and the risks attending 
naked lights went on as merrily as ever. 

In order to avoid explosions in mines which 
were known to give off large quantities of gas, 
" fiery " pits as they are called, Sir Humphry 
Davy in 1815 invented his safety lamp, the prin- 
ciple of which can be stated in a few words. 

If a piece of fine wire gauze be held over a 



THE COAL-MINE AND ITS DANGERS. gi 

gas-jet before it is lit, and the gas be then turned 
on, it can be lit above the gauze, but the flame 
will not pass downwards towards the source of 
the gas; at least, not until the gauze has become 
over-heated. The metallic gauze so rapidly con- 
ducts away the heat, that the temperature of the 
gas beneath the gauze is unable to arrive at the 
point of ignition. In the safety-lamp the little 
oil-lamp is placed in a circular funnel of fine 
gauze, which prevents the flame from passing 
through it to any explosive gas that may be 
floating about outside, but at the same time al- 
lows the rays of light to pass through readily. 
Sir Humphry Davy, in introducing his lamp, cau- 
tioned the miners against exposing it to a rapid 
current of air, which would operate in such a 
way as to force the flame through the gauze, 
and also against allowing the gauze to become 
red-hot. In order to minimize, as far as possible, 
the necessity of such caution the lamp has been 
considerably modified since first invented, the 
speed of the ventilating currents not now allow- 
ing of the use of the simple Davy lamp, but the 
principle is the same. 

During the progress of Sir Humphry Davy's 
experiments, he found that when fire-damp was 
diluted with 85 per cent, of air, and any less 
proportion, it simply ignited without explosion. 
With between 85 per cent, and 89 per cent, of 
air, fire-damp assumed its most explosive form, 
but afterwards decreased in explosiveness, until 
with 94-i per cent, of air it again simply ignited 
without explosion. With between 11 and 12 per 
cent, of fire-damp the mixture was most danger- 
ous. Pure fire-damp itself, therefore, is not dan- 
gerous, so that when a small quantity enters the 



92 



THE STORY OF A PIECE OF COAL. 



gauze which surrounds the Davy lamp, it simply 
burns with its characteristic blue flame, but at the 
same time gives the miner due notice 
of the danger which he was running. 

With the complicated improve- 
ments which have since been made 
in the Davy lamp, a state of almost 





Fig. 32. — Gas Jet and Davy Lamp. 

absolute safety can be guaranteed, but still from 
time to time explosions are reported. Of the 
cause of many we are absolutely ignorant, but 
occasionally a light is thrown upon their origin 
by a paragraph appearing in a daily paper. Two 
men are charged before the magistrates with 
being in the possession of keys used exclusively 
for unlocking their miners' safety-lamps. There 
is no defence. These men know that they carry 
their lives in their hands, yet will risk their 
own and those of hundreds of others, in order 
that they may be able to light their pipes by 
means of their safety-lamps. Sometimes in an 
unexpected moment there is a great dislodgment 



THE COAL-MINE AND ITS DANGERS. 93 

of coal, and a tremendous quantity of gas is set 
free, which may be sufficient to foul the passages 
for some distance around. The introduction or 
-exposure of a naked light for even so much as a 
second is sufficient to cause explosion of the mass ; 
doors are blown down, props and tubbing are 
charred up, and the volume of smoke, rushing up 
by the nearest shaft and overthrowing the engine- 
house and other structures at the mouth, con- 
veys its own sad message to those at the surface, of 
the dreadful catastrophe that has happened below. 
Perhaps all that remains of some of the workers 
consists of charred and scorched bodies, scarcely 
recognisable as human beings. Others escape 
with scorched arms or legs, and singed hair, to 
tell the terrible tale to those who were more for- 
tunately absent ; to speak of their own sufferings 
when, after having escaped the worst effects of 
the explosion, they encountered the asphyxiating 
rush of the after-damp or choke-damp, which 
had been caused by the combustion of the fire- 
damp. " Choke-damp " in very truth it is, for it 
is principally composed of our old acquaintance 
carbonic acid gas (carbon dioxide), which is well 
known as a non-supporter of combustion, and as 
an asphyxiator of animal life. 

It seems a terrible thing that on occasions the 
workings and walls themselves of the coal-mine 
catch fire and burn incessantly. Yet such is the 
case. Years ago this happened in the case of an 
old colliery near Dudley, at the surface of which, 
by means of the heat and steam thus afforded, 
early potatoes for the London market, we are 
told, were grown ; and it was no unusual thing to 
see the smoke emerging from cracks and crevices 
in the rocks in the vicinity of the town. 



94 



THE STORY OF A PIECE OF COAL. 



From fire on the one hand, we pass, on the 
other, to the danger which awaits miners from a 
sudden inrush of water. During the great coal 
strike of 1893, certain mines became unworkable 
in consequence of the quantity of water which 
flooded the mines and which, continually passing 
along the natural fractures in the earth's crust, 
is always ready to find a storage reservoir in the 
workings of a coal-mine. This is a difficulty 
which is always experienced in the sinking of 
shafts, and the shutting off of water engages 
the best efforts of mining engineers. 

Added to these various dangers which exist in 
the coal-mine, we must not omit to notice those 
accidents that are continually being caused by 
the falling-in of roofs or of walls, from the falling 
of insecure timber, or of what are known as " coal- 
pipes " or "bell-moulds." Then, again, every 
man that enters the mine trusts his life to the 
cage by which he descends to his labour, and 
shaft accidents are not infrequent. 



Causes of Death. 



Deaths resulting from fire-damp ex- 
plosions 

Deaths resulting from falling roofs 
and coals 

Deaths resulting from shaft acci- 
dents 

Deaths resulting from miscellaneous 
causes and above ground 



No. of 
Deaths. 



2019 

3953 
I7IO 
2234 



9916 



Proportion 
per cent. 



20.36 

39-87 
17.24 

22.53 



The above table shows the number of deaths 
from colliery accidents in England for ten years, 



THE COAL-MINE AND ITS DANGERS. 95 

compiled by a Government inspector, and from 
this it will be seen that those resulting from fall- 
ing roofs number considerably more than one- 
third of the whole. 

Every reader of the daily papers is familiar 
with the harrowing accounts which are there 
given of coal-mine explosions. 

This kind of accident is one, which is, above 
all, associated in the public mind with the dan- 
gers of the coal-pit. Yet the accidents arising 
from this cause number but 20 per cent, of those 
recorded, and granted there be proper inspection, 
and the use of naked lights be absolutely abol- 
ished, this low per centage might still be consider- 
ably reduced. 

A terrific explosion occurred at Whitwick Col- 
liery, Leicestershire, in 1893, when two lads were 
killed, whilst a third was rescued after a very 
narrow escape. The lads, it is stated, were work- 
ing with naked lights, when a sudden fall of coal 
released a quantity of gas, and an immediate ex- 
plosion was the natural result. Accidents had 
been so rare at this pit that it was regarded as 
particularly safe, and it was alleged that the use 
of naked lights was not uncommon. 

This is an instance of that large number of 
accidents which are undoubtedly preventable. 

An interesting commentary on the careless 
manner in which miners risk their lives was 
shown in the discoveries made after an explosion 
at a colliery near Wrexham in 1889. Near the 
scene of the explosion an unsecured safety-lamp 
was found, and the general opinion at the time 
was that the disaster was caused by the inex- 
cusable carelessness of one of the twenty vic- 
tims. Besides this, when the clothing of the 



g6 THE STORY OF A PIECE OF COAL. 

bodies recovered was searched, the contents, 
taken, it should be noted, with the pitmen into 
the mines, consisted of pipes, tobacco, matches, 
and even keys for unlocking the lamps. It is a 
strange reflection on the manner in which this 
mine had been examined previous to the men en- 
tering upon their work, that the underlooker, but 
half an hour previously, had reported the pit to 
be free from gas. 

Another instance of the same foolhardiness on 
the part of the miners is contained in the report 
issued in regard to an explosion which occurred 
at Denny, in Stirlingshire, on April 26th, 1895. 
By this accident thirteen men lost their lives, and 
upon the bodies of eight of the number the fol- 
lowing articles were found : Upon Patrick Carr, 
tin matchbox half full of matches and a contri- 
vance for opening lamps ; John Comrie, split nail 
for opening lamps; Peter Conway, seven matches 
and split key for opening lamps ; Patrick Dunton, 
split nail for opening lamps ; John Herron, clay 
pipe and piece of tobacco ; Henry M'Govern, tin 
matchbox half full of matches ; Robert Mitchell, 
clay pipe and piece of tobacco ; John Nicol, 
wooden pipe, piece of tobacco, one match, and 
box half full of matches. The report stated that 
the immediate cause of the disaster was the igni- 
tion of fire-damp by naked light, the conditions 
of temperature being such as to exclude the possi- 
bility of spontaneous combustion. Henry M'Gov- 
ern had previously been convicted of having a 
pipe in the mine. With regard to the question of 
sufficient ventilation it continued: — "And we are 
therefore led, on a consideration of the whole 
evidence, to the conclusion that the accident can- 
not be attributed to the absence of ventilation, 



THE COAL-MINE AND ITS DANGERS. 97 

which the mine owners were bound under the- 
Mines Regulation Act and the special rules to* 
provide." The report concluded as follows : — 
" On the whole matter we have to report that, in. 
our opinion, the explosion at Quarter Pit oa 
April 26th, 1895, resulting in the loss of thirteen 
lives, was caused by the ignition of an accumula- 
tion or an outburst of gas coming in contact with- 
a naked light, ' other than an open safety-lamp/ 
which had been unlawfully kindled by one of the 
miners who were killed. In our opinion, the in- 
tensity of the explosion was aggravated, and its- 
area extended, by the ignition of coal-dust. ,, 

We have mentioned that accidents have fre- 
quently occurred from the falling of " coal-pipes," 
or, as they are also called, "bell-moulds." We 
must explain what is meant by this term. They 
are simply what appear to be solid trunks of 
trees metamorphosed into coal. If we go into a 
tropical forest we find that the woody fibre of 
dead trees almost invariably decays faster than 
the bark, The result is that what may appear to 
be a sound tree is nothing but an empty cylinder 
of bark. This appears to have been the case 
with many of the trees in coal-mines, where they 
are seen to pierce the strata, and around which 
the miners are excavating the coal. As the coaly 
mass collected around the trunk when the coal 
was being formed, the interior was undergoing a. 
process of decomposition, while the bark assumed 
the form of coal. The hollow interior then be- 
came filled with the shale or sandstone which 
forms the roof of the coal, and its sole support 
when the coal is removed from around it, is the 
thin rind of carbonised bark. When this falls to 
pieces, or loses its cohesion, the sandstone trunk: 



9 8 



THE STORY OF A PIECE OF COAL. 




falls of its own weight, often causing the death 
of the man that works beneath it. Sir Charles 

Lyell mentions that in 
a colliery near Newcas- 
tle, no less than thirty 
sigillaria trees were 
standing in their nat- 
ural position in an area 
of fifty yards square, 
the interior in each 
case being sandstone, 
which was surrounded 
by a bark of friable 
coal. 

The last great dan- 
ger to which we have 
here to make reference, 
is the explosive action 
of a quantity of coal- 
dust in a dry condition. 
It is only now com- 
mencing to be fully 
recognised that this is 
really a most dangerous 
Fig. 33 -Part of a trunk of Sig- explosive. As we have 

illana, showing the thin out- i 

er carbonised bark, with leaf- seen > large quantities 

scars, and the seal-like im- of COal are "formed al- 

r'emTv'ed 5 where the **"* ** most exclusively of Up- 

idode?idron spores, and 
such coal is productive of a great quantity of 
dust. Explosions which are always more or less 
attributable to the effects of coal-dust are gener- 
ally considered, in the official statistics, to have 
been caused by fire-damp. The Act regulating 
mines in Great Britain is scarcely up to date in 
this respect. There is a regulation which pro- 



THE COAL-MINE AND ITS DANGERS. 99 

vides for the watering of all dry and dusty places 
within twenty yards from the spot where a shot 
is fired, but the enforcement of this regulation in 
each and every pit necessarily devolves on the 
managers, many of whom in the absence of an 
inspector leave the requirement a dead letter. 
Every improvement which results in the better 
ventilation of a coal-mine tends to leave the dust 
in a more dangerous condition. The air, as it 
descends the shaft and permeates the workings, 
becomes more and more heated, and licks up 
every particle of moisture it can touch. Thor- 
ough ventilation results in more greatly freeing 
a mine of the dangerous fire-damp, but the remedy 
brings about another disease, viz., the drying-up 
of all moisture. The dust is thus left in a dan- 
gerously inflammable condition, acting like a 
train of gunpowder, to be started, it may be, by 
the slightest breath of an explosion. There is 
apparently little doubt that the presence of coal- 
dust in a dry state in a mine appreciably increases 
the liability of explosion in that mine. 

So far as Great Britain is concerned, a Royal 
Commission was appointed by Lord Rosebery's 
Government to inquire into and investigate the 
facts referring to coal-dust. Generally speaking, 
the conclusion arrived at was that fine coal-dust 
was inflammable under certain conditions. There 
was considerable difference of opinion as to what 
these conditions were. Some were of opinion 
that coal-dust and air alone were of an explosive 
nature, whilst others thought that alone they were 
not, but that the addition of a small quantity of 
fire-damp rendered the mixture explosive. An 
important conclusion was come to, that, with the 
combustion of coal-dust alone, there was little or 



IOO THE STORY OF A PIECE OF COAL. 

no concussion, and that the flame was not of an 
explosive character. 

Coal-dust was, however, admittedly dangerous, 
especially if in a dry condition. The effects of 
an explosion of gas might be considerably ex- 
tended by its presence, and there seems every 
reason to believe that, with a suitable admixture 
of air and a very small proportion of gas, it forms 
a dangerous explosive. Legislation in the direc- 
tion of the report of the Commission is urgently 
needed. 

We have seen elsewhere what it is in the dust 
which makes it dangerous, how that, for the most 
part, it consists of the dust-like spores of the 
lepidodendron tree, fine and impalpable as the 
spores on the backs of some of our living ferns, 
and the fact that this consists of a large propor^ 
tion of resin makes it the easily inflammable sub- 
stance it is. No explosion in the anthracite 
region of Pennsylvania has ever been traced with 
certainty to coal-dust, and it is only in very dry 
mines that bituminous dust can be explosive. In 
1888, however, there was an explosion of coal- 
dust in a bituminous coal-mine at Pittsburg, Kan., 
by which over a hundred lives were lost. 

In some of the pits in South Wales a system 
of fine sprays of water is in use, by which the 
water is ejected from pin-holes pricked in a series 
of pipes which are carried through the workings. 
A fine mist is thus caused where necessary, which 
is carried forward by the force of the ventilating 
current. 

A thorough system of inspection in coal- 
mines throughout the world is undoubtedly 
urgently called for, in order to ensure the proper 
carrying out of the various regulations framed for 



EARLY HISTORY— ITS USE AND ITS ABUSE. IOI 

their safety. It is extremely unfortunate that so 
many of the accidents which happen are pre- 
ventable, if only men of knowledge and of scien- 
tific attainments filled the responsible positions 
of the overlookers. 



CHAPTER V. 

EARLY HISTORY — ITS USE AND ITS ABUSE. 

The extensive use of coal throughout the 
civilised world for purposes of heating and illumi- 
nation, and for the carrying on of manufactures 
and industries, may be regarded as a well-marked 
characteristic of the age in which we live. 

Coal must have been in centuries past a 
familiar object to many generations. People 
must have long been living in close proximity to 
its outcrops at the sides of the mountains and at 
the surface of the land, yet without being ac- 
quainted with its practical value, and it seems 
strange that so little use was made of it until 
about three centuries ago, and that its use did 
not spread earlier and more quickly throughout 
civilised countries. 

A mineral fuel is mentioned by Theophrastus 
about 300 b. c, from which it is inferred that 
thus early it was dug from some of the more 
shallow depths. The Britons before the time of 
the Roman invasion are credited with some 
slight knowledge of its industrial value. Pre- 
historic excavations have been found in Mon- 
mouthshire, and at Stanley, in Derbyshire, and 
the flint axes there actually found imbedded in 



102 THE STORY OF A PIECE OF COAL. 

the layer of coal are reasonably held to indicate 
its excavation by neolithic or palaeolithic (stone- 
age) workmen. 

The fact that coal cinders have been found on 
old Roman walls in conjunction with Roman 
tools and implements, goes to prove that its use, 
at least for heating purposes, was known in Eng- 
land prior to the Saxon invasion, whilst some 
polygonal chambers in the six-foot seam near 
the river Douglas, in Lancashire, are supposed 
also to be Roman. 

V The Chinese were early acquainted with the 
existence of coal, and knew of its industrial 
value to the extent of using it for the baking of 
porcelain. 

The fact of its extensive existence in Great 
Britain, and the valuable uses to which it might 
be put, did not, however, meet with much notice 
. until the ninth century, when, owing to the de- 
crease of the forest-area, and consequently of the 
supply of wood-charcoal therefrom, it began to 
attract attention as affording an excellent substi- 
tute for charcoal. 

The coal-miner was, however, still a creation 
of the future, and even as peat is collected in Ire- 
land at the present day for fuel, without the la- 
borious process of mining for it, so those people 
living in coal-bearing districts found their needs 
satisfied by the quantity of coal, small as it was, 
which appeared ready to hand on the sides of the 
carboniferous mountains. Till then, and for a 
long time afterwards, the principal source of fuel 
consisted of vast forests, amidst which the char- 
coal-burners, or " colliers " as they were even then 
called, lived out their lonely existence in preparing 
charcoal and hewing wood, for the fires of the 



EARLY HISTORY— ITS USE AND ITS ABUSE. 103 

baronial halls and stately castles then swarming 
throughout the land. As the forests became used 
up, recourse was had more and more to coal, and 
in 1239 the first charter dealing with and recognis- 
ing the importance of the supplies was granted 
to the freemen of Newcastle, according them 
permission to dig for coals in the Castle fields. 
About the same time a coal-pit at Preston, Had- 
dingtonshire, was granted to the monks of New- 
battle. 
/>! Specimens of Newcastle coal were sent to 
London, but the city was loth to adopt its use, 
objecting to the innovation as one prejudicial 
to the health of its citizens. By the end of the 
16th century, two ships only were found sufficient 
to satisfy the demand for stone-coal in London. 
This slow progress may, perhaps, have been par- 
tially owing to the difficulties which were placed 
in the way of its universal use. Great opposition 
was experienced by those who imported it into 
the metropolis, and the increasing amount which 
was used by brewers and others about the year 
1300, caused serious complaints to be made, the 
effect of which was to induce Parliament to obtain 
a proclamation from the King prohibiting its use, 
and empowering the justices to inflict a fine on 
those who persisted in burning it. The nuisance 
which coal has since proved itself, in England by 
polluting the atmosphere and by denuding wide 
tracts of country of all vegetation, was even thus 
early recognised, and had the efforts which were 
then made to stamp out its use, proved successful, 
those who live now in the great cities might never 
have become acquainted with that species of 
black winter fog which at times hangs like a pall 
over them, and transforms the brightness of day 



104 THE STORY OF A PIECE OF COAL. 

into a darkness little removed from that of night. 
At the same time, we must bear in mind that it is 
universally acknowledged that England owes her 
prosperity, and her pre-eminence in commerce, in 
great part, to her happy possession of wide and 
valuable coal-fields, and many authorities have 
not hesitated to say, that, in their opinion, the 
length of time during which England will con- 
tinue to hold her prominent position as an in- 
dustrial nation is limited by the time during which 
her coal will last. 

The attempt to prohibit the burning of coal 
was not, however, very successful, for in the 
reign of Edward III. a license was again granted 
to the freemen of Newcastle to dig for coals. 
Newcastle was thus the first town to become 
famous as the home of the coal-miner, and the 
fame which it early acquired, it has held unceas- 
ingly ever since. 

Other attempts at prohibition of the article 
were made at various times subsequently, amongst 
them being one which was made in Elizabeth's 
reign. It was supposed that the health of the 
country squires, who came to town to attend the 
session of Parliament, suffered considerably dur- 
ing their sojourn in London, and, to remedy this 
serious state of affairs, the use of stone-coal dur- 
ing the time Parliament was sitting was once more 
prohibited. 

Coal was, however, by this time beginning to 
be recognised as a most valuable and useful 
article of fuel, and had taken a position in the 
industrial life of the country from which it was 
difficult to remove it. Rather than attempt to 
have arrested the growing use of coal, Parlia- 
ment would have been better employed had it 



EARLY HISTORY— ITS USE AND ITS ABUSE. 105 

framed laws compelling the manufacturers and 
other large burners to consume their own smoke, 
and instead of aiming at total prohibition, have 
encouraged an intelligent and more economical 
use of it. 

In spite of all prohibition its use rapidly- 
spread, and it was soon applied to the smelting 
of iron and to other purposes. Iron had been 
largely produced in the south of England from 
strata of the Wealden formation, during the ex- 
istence of the great forest which at one time ex- 
tended for miles throughout Surrey and Sussex. 
The discovery of coal, however, and the opening 
up of many mines in the north, gave an important 
impetus to the smelting of iron in those counties, 
and as the forests of the Weald became exhausted, 
the iron trade gradually declined. Furnace after 
furnace became extinguished, until in 1809 that 
at Ashburnham, which had lingered on for some 
years, was compelled to bow to the inevitable 
fate which had overtaken the rest of the iron 
blast-furnaces. 

Bituminous coal was mined in Virginia about 
1750 and around Pittsburg, Pa., before 1760. 
Pittsburg coal was in general use in the region 
round about the mines at the beginning of the 
nineteenth century both for manufacturing and 
household purposes, and shipments to Philadelphia 
soon began. Much difficulty was met with in 
bringing anthracite into use in America. It was 
discovered near Wilkes Barre in 1762, but being 
much harder than the kind they had known in 
England the colonists were unable to make it 
burn. It was first successfully used in black- 
smiths' forges, with the aid of the bellows, and 
was employed in the Pennsylvania armory at 



106 THE STORY OF A PIECE OF COAL. 

Carlisle in the manufacture of firearms for the 
Continental troops during the Revolution. Coal 
was found also in other parts of the anthracite 
region between 1790 and 1826. Each of the 
earlier mine-owners in turn tried to make a 
market for the mineral in Philadelphia, but all 
met with failure until they introduced specially 
adapted grates and their customers learned, gen- 
erally by accident, that an anthracite fire must 
not be poked incessantly. But progress was still 
slow, so that in 1820 the 365 tons sent from the 
Lehigh region were enough to supply the market. 
In 1831, however, the shipments from this district 
had advanced to 40,000 tons, and in 1892 to nearly 
6,500,000. 

Anthracite coal is practically free from the iron 
pyrites which gives off the sulphurous fumes so 
much complained of in England, and the little 
smoke yielded by American anthracite readily 
passes away in the drier air of this country. 

In his interesting work, " Sylvia," published 
in 1661, Evelyn, in speaking of the noxious 
vapours poured out into the air by the increas- 
ing number of coal fires, writes, " This is that 
pernicious smoke which sullies all her glory, 
superinducing a sooty crust or furr upon all that 
it lights, spoiling movables, tarnishingthe plate, 
gildings and furniture, and corroding the very 
iron bars and hardest stones with those piercing 
and acrimonious spirits which accompany its 
sulphur, and executing more in one year than 
the pure air of the country could effect in some 
hundreds." The evils here mentioned are those 
which have grown and have become intensified 
a hundred-fold during the two centuries and a 
half which have since elapsed. When the many 



EARLY HISTORY— ITS USE AND ITS ABUSE. 107 

efforts which were made to limit its use in the 
years prior to 1600 are remembered; at which 
time, we are informed, two ships only were engaged 
in bringing coal to London, it at once appears 
how paltry are the efforts made now to moderate 
these same baneful influences on the atmosphere, 
at a time when the annual consumption of coal 
in the United Kingdom has reached the enormous 
total of 190 millions of tons. The various smoke- 
abatement associations which have started into 
existence during the last few years are doing 
a little, although very little, towards directing 
popular attention to the subject; but there is an 
enormous task before them, that of awakening 
every individual to an appreciation of the per- 
sonal interest which he has in their success, and 
to realise how much might at once be done if 
each were to do his share, minute though it might 
be, towards mitigating the evils of the present 
mode of coal-consumption. Probably very few 
householders ever realise what important factors 
their chimneys constitute, in bringing about air 
pollution, and the more they do away with the 
use of bituminous coal for fuel, the nearer they 
will be to the time when the English yellow fog 
will be a thing of the past. 

A large proportion of smoke consists of parti- 
cles of pure unconsumed carbon, and this is ac- 
companied by sulphurous acid, begotten by the 
sulphur which is contained in the coal ordinarily 
used in England to the amount of about eight 
pounds in every thousand ; by sulphuretted hy- 
drogen, by hydro-carbons, and by vapours of 
various kinds of oils, small quantities of ammonia, 
and other bodies not by any means contributing 
to a healthy condition of the atmosphere. A 



108 THE STORY OF A PIECE OF COAL. 

good deal of the heavier carbon is deposited 
along the walls of chimneys in the form of soot, 
together with a small percentage of sulphur of 
ammonia ; this is as a consequence very generally 
used for manure. The remainder is poured out 
into the atmosphere, there to undergo fresh 
changes, and to become a fruitful cause of those 
thick black fogs with which town-dwellers are so 
familiar. Sulphuretted hydrogen (H 2 S) is a gas 
well known to students of chemistry as a most 
powerful reagent, its most characteristic external 
property being the extremely offensive odour 
which it possesses, and which bears a strong 
resemblance to that of rotten eggs or decompos- 
ing fish. It tarnishes silver work and picture 
frames very rapidly. On combustion it changes 
to sulphurous acid (S0 2 ), and this in turn has 
the power of taking up from the air anothe: 
atom of oxygen, forming sulphuric acid (S0 3 -f 
water), or, as we more familiarly know it, oil oi 
vitriol. 

Yet the smoke itself, including as it does all 
the many impurities which exist in coal, is not 
only evil in itself, but is evil in its influences. Dr. 
Siemens has said : — " It has been shown that the 
fine dust resulting from the imperfect combustion 
of coal was mainly instrumental in the formation 
of fog; each particle of solid matter attracting 
to itself aqueous vapour. These globules of fog 
were rendered particularly tenacious and dis- 
agreeable by the presence of tar vapour, another 
result of imperfect combustion of raw fuel, which 
might be turned to better account at the dye- 
works. The hurtful influence of smoke upon 
public health, the great personal discomfort to 
which it gave rise, and the vast expense it 



EARLY HISTORY— ITS USE AND ITS ABUSE. 109 

indirectly caused through the destruction of our 
monuments, pictures, furniture, and apparel, were 
now being recognised/* 

The most effectual remedy would result from 
a general recognition of the fact that wherever 
smoke was produced, fuel was being consumed 
wastefully, and that all our calorific effects, from 
the largest furnace to the domestic fire, could be 
realised as completely, and more economically, 
without allowing any of the fuel employed to reach 
the atmosphere unburnt. This most desirable 
result might be effected by the use of gas for all 
heating purposes, with or without the additional 
use of coke or anthracite. The success of the so- 
called smoke-consuming stoves is greatly open to 
question, whilst some of them have been reported 
upon by those appointed to inspect them as ac- 
tually accentuating the incomplete combustion, 
the abolition of which they were invented to bring 
about. 

The smoke nuisance is one which cuts at the 
very basis of business life where it prevails. The 
cloud which, under certain atmospheric condi- 
tions, rests like a pall over the great cities of 
England and the central United States, will not 
even permit at times of a single ray of sunshine 
permeating it. No one knows at what hour to 
expect it. It is like a giant spectre which, hav- 
ing lain dormant since the carboniferous age, has 
been raised into life and being at the call of rest- 
less humanity ; it is now punishing those who 
have summoned it to their service by clasping 
them in its deadly arms, cutting off the brilliant 
sunshine, and necessitating the use in the day- 
time of artificial light; inducing all kinds of bron- 
chial and throat affections, corroding telegraph 



IIO THE STORY OF A PIECE OF COAL. 

and telephone wires, and weathering away the 
masonry of public buildings. 

V The immense value to us of the coal-deposits 
which lie buried in such profusion in the earth 
beneath us, can only be appreciated when we con- 
sider the many uses to which coal has been put. 
We must remember, as we watch the ever-ex- 
tending railway ramifying the country in every 
direction, that the first railway and the first 
locomotive ever built, were those which were 
brought into being in 1814 by George Stephen- 
son, for the purpose of the carriage of coals from 
the Killingworth Colliery. To the importance of 
coal in our manufactures, therefore, we owe the 
subsequent development of steam locomotive 
power as the means of the introduction of 
passenger traffic, and by the use of coal we are 
enabled to travel from one end of the country to 
the other in a space of time inconceivably small 
as compared with that occupied on the same 
journey in the old coaching days. The increased 
rapidity with which our vessels cross the wide 
ocean we owe to the use of coal ; our mines are 
carried to greater depths owing to the power our 
pumping-engines obtain from coal in clearing 
the mines of water and in ensuring ventilation ; 
the enormous development of the iron trade only 
became possible with the increased blast power 
obtained from the consumption of coal, and the 
very hulls and engines of our steamships are 
made of this iron ; our railroads and engines are 
mostly of iron, and when we think of the exten- 
sive use of iron utensils in every walk of life, we 
see how important becomes the power we possess 
of obtaining the necessary fuel to feed the smelt- 
ing furnaces. Evaporation by the sun was at 



HOW GAS IS MADE, ETC. Ill 

one time the sole means of obtaining salt from 
sea-water ; now coal is used to boil the salt pans 
and to purify the brine from the salt-mines of 
Michigan or New York. The extent to which 
gas is used for illuminating purposes reminds us 
of another important product obtained from 
coal. Paraffin oil and petroleum may be obtained 
from it, whilst candles, oils, dyes, lubricants, and 
many other useful articles go to attest the impor- 
tance of the underground stores of that mineral 
which has well and deservedly been termed the 
" black diamond." 



CHAPTER VI. 

HOW GAS IS MADE — ILLUMINATING OILS AND 
BYE-PRODUCTS. 

Accustomed as we are at the present day to 
see street after street of well-lighted thorough- 
fares, brilliantly illuminated by gas-lamps main- 
tained by public authority, we can scarcely appre- 
ciate the fact that the use of gas is, comparatively 
speaking, of but recent growth, and that, like 
the use of coal itself, it has not yet existed a 
century in public favour. Valuable as coal is 
in very many different ways, perhaps next in 
value to its actual use as fuel, ranks the use of 
the immediate product of its distillation — viz., 
gas ; and although gas is in some respects wan- 
ing before the march of the electric light in our 
day, yet, even as gas at no time has altogether 
superseded old-fashioned oil, so we need not 



112 THE STORY OF A PIECE OF COAL. 

anticipate a time when gas in turn will be likely 
to be superseded by the electric light, there 
being many uses to which the one may be put, to 
which the latter would be altogether inapplicable ; 
for, in the words of Dr. Siemens, assuming the 
cost of electric light to be practically the same 
as gas, the preference for one or other would in 
each application be decided upon grounds of rela- 
tive convenience, but gas-lighting would hold its 
own as the poor man's friend. Gas is an institu- 
tion of the utmost value to the artisan ; it re- 
quires hardly any attention, is supplied upon 
regulated terms, and gives, with what should be a 
cheerful light, a genial warmth, which often saves 
the lighting of a fire. 

The revolution which gas has made in the ap- 
pearance of the streets, where formerly the only 
illumination was that provided by each house- 
holder, who, according to his means, hung out a 
more or less efficient lantern, and consequently a 
more or less smoky one, cannot fail also to have 
brought about a revolution in the social aspects 
of the streets, and therefore is worthy to be 
ranked as a social reforming agent ; and some 
slight knowledge of the process of its manufac- 
ture, such as it is here proposed to give, should 
be in the possession of every educated individual. 
Yet the subjects which must be dealt with in this 
chapter are so numerous and of such general in- 
terest, that we shall be unable to enter more than 
superficially into any one part of the whole, but 
shall strive to give a clear and comprehensive 
view, which shall satisfy the inquirer who is not a 
specialist. 

The credit of the first attempt at utilising the 
gaseous product of coal for illumination appears 



HOW GAS IS MADE, ETC. 113 

to be due to Murdock, an engineer at Redruth, 
who, in 1792, introduced it into his house and 
offices, and who, ten years afterwards, as the re- 
sult of numerous experiments which he made 
with a view to its utilisation, made a public dis- 
play at Birmingham on the occasion of the Peace 
of Amiens, in 1802. 

More than a century before, however, the gas 
obtained from coal had been experimented upon 
by a Dr. Clayton, who, about 1690, conceived the 
idea of heating coal until its gaseous constituents 
were forced out of it. He described how he ob- 
tained steam first of all, then a black oil, and 
finally a " spirit," as our ancestors were wont to 
term the gas. This, to his surprise, ignited on a 
light being applied to it, and he considerably 
amused his friends with the wonders of this in- 
flammatory spirit. For a century afterwards it 
remained in its early condition, a chemical won- 
der, a thing to be amused with ; but it required 
the true genius and energy of Murdock to show 
the great things of which it was capable. 

London received its first instalment of gas in 
1807, and during the next few years its use be- 
came more and more extended, houses and streets 
rapidly receiving supplies in quick succession. It 
was not, however, till about the year 1820 that its 
use throughout the country became at all gen- 
eral, St. James' Park being gas-lit in the succeed- 
ing year. Little more than eighty years ago, 
and amongst the many wonderful things which 
sprung up during the nineteenth century, perhaps 
we may place in the foremost rank for actual 
utility, the gas extracted from coal, conveyed as 
it is through miles upon miles of underground 
pipes into the very homes of the people, and con- 
8 



114 



THE STORY OF A PIECE OF COAL. 



stituting now almost as much a necessity of a 
comfortable existence as water itself. 




FlG. 34. — Inside a Gas-Holder. 

The use of gas thus rapidiy extended for illu 
minating purposes, and to a very great extent 



HOW GAS IS MADE, ETC. 115 

superseded the old-fashioned means of illumina- 
tion. 

The gas companies which sprang up were not 
slow to notice that, seeing the gas was supplied 
by meter, it was to their pecuniary advantage " to 
give merely the prescribed illuminating power, 
and to discourage the invention of economical 
burners, in order that the consumption might 
reach a maximum. The application of gas for 
heating purposes had not been encouraged, and 
was still made difficult in consequence of the ob- 
jectionable practice of reducing the pressure in 
the mains during daytime to the lowest possible 
point consistent with prevention of atmospheric 
indraught/' 

The introduction of an important rival into 
the field in the shape of the electric light has now 
given a powerful impetus to the invention and J 
introduction of effective gas-lamps, and various 
appliances for effecting savings in the amount of 
gas consumed or giving greater efficiency are 
now widely advertised. As. long as gas retained 
almost the monopoly, there was no incentive to 
the gas companies to produce an effective light 
cheaply ; but now that the question of the rela- 
tive cheapness of gas and electricity is being 
actively discussed, the gas companies, true to the 
instinct of self-preservation, seem determined to 
show what can be done when gas is consumed in 
a scientific manner. 

In order to understand how best a burner 
should be constructed in order that the gas that 
is burnt should give the greatest possible amount 
of illumination, let us consider for a moment the 
composition of the gas flame. It consists of 
three parts, (1) an interior dark space, in which 



Il6 THE STORY OF A PIECE OF COAL. 

the elements of the gas are in an unconsumed 
state ; (2) an inner ring around the former, whence 
the greatest amount of light is obtained, and in 
which are numerous particles of carbon at a white 
heat, each awaiting a supply of oxygen in order 
to bring about combustion ; and (3) an outer ring 
of blue flame in which complete combustion has 
taken place, and from which the largest amount 
of heat is evolved. 

The second of these portions of the flame cor- 
responds with the " reducing " flame of the blow- 
pipe, since this part, if turned upon an oxide, will 
reduce it, i. e., abstract its oxygen from it. This 
part also corresponds with the jet of the Bunsen 
burner, w T hen the holes are closed by which other- 
wise air would mingle with the gas, or with the 
flame from a gas-stove when the gas ignites be- 
neath the proper igniting-jets, and which gives 
consequently a white or yellow flame. 

The third portion, on the other hand, corre- 
sponds with the " oxidising " flame of the blow- 
pipe, since it gives up oxygen to bodies that are 
thirsting for it. This also corresponds with the 
ordinary blue flame of the Bunsen burner, and 
with the blue flame of gas-stoves where heat, and 
not light, is required, the blue flame in both 
cases being caused by the admixture of air with 
the gas. 

Thus, in order that gas may give the best 
illumination, we must increase the yellow or white 
space of carbon particles at a white heat, and a 
burner that will do this, and at the same time 
hold the balance so that unconsumed particles of 
carbon shall not escape in the w r ay of smoke, will 
give the most successful illuminating results. 
With this end in view the addition of albo-carbon 



HOW GAS IS MADE, ETC. 117 

to a bulb in the gas-pipe has proved very success- 
ful, and the incandescent gas-jet is constructed 
on exactly the same chemical principle. The in- 
vention of burners which brought about this de- 
sirable end has doubtless not been without effect 
in acting as a powerful obstacle to the wide- 
spread introduction of the electric light. 

Without entering into details of the manufac- 
ture of gas, it will be as well just to glance at 
the principal parts of the apparatus used. 

The gasometer, as it has erroneously been 
called, is a familiar object to most people, not 
only to sight, but unfortunately also to the organs 
of smell. It is in reality of course only the gas- 
holder, in which the final product of distillation 
of the coal is stored, and from which the gas im- 
mediately passes into the distributing mains. 

The first, and perhaps most important, portion 
of the apparatus used in gas-making, is the series. 
of retorts into which the 'coal is placed, and from 
which, by the application of heat, the various 
volatile products distil" over. These retorts are 
huge cast-iron vessels, encased in strong brick- 
work, usually five in a group, and beneath which 
a large furnace is kept going until the process is 
complete. Each retort has an iron exit pipe 
affixed to it, through which the gases generated 
by the furnace are carried off. The exit pipes 
all empty themselves into what is known as the 
hydraulic main, a long horizontal cylinder, and in 
this the gas begins to deposit a portion of its 
impurities. The immediate products of distilla- 
tion are, after steam and air, gas, tar, ammoniacal 
liquor, sulphur in various forms, and coke, the 
last being left behind in the retort. In the hy- 
draulic main some of the tar and ammoniacal 



n8 



THE STORY OF A PIECE OF COAL. 






liquor already begin to be deposited. The gas 
passes on to the condenser, which consists of a 




Fig. 35.— Filling Retorts by Machinery. 

number of U-shaped pipes. Here the impurities 
are still further condensed out, and are collected 
in the tar-pit whilst the gas proceeds, still further 
lightened of its impurities. It may be mentioned 



HOW GAS IS MADE, ETC. 



II 9 



that the temperature of the gas in the condenser 
is reduced to about 6o° F., but below this some 
of the most valuable of the illuminants of coal- 
gas would commence to be deposited in liquid 
form, and care has to be taken to prevent a. 
greater lowering of temperature. A mechanical 
contrivance known as the exhauster is next used,, 
by which the gas is, amongst other things, helped 
forward in its onward movement through the ap- 
paratus. The gas then passes to the washers or 




Fig. 36. 



scrubbers, a series of tall towers, from which water 
is allowed to fall as a fine spray, and by means of 
which large quantities of ammonia, sulphuretted 
hydrogen, carbonic acid and oxide, and cyanogen 
compounds, are removed. In the scrubber the 
water used in keeping the coke, with which it is 
filled, damp, absorbs these compounds, and the 
union of the ammonia with certain of them takes 
place, resulting in the formation of carbonate of 
ammonia (smelling salts), sulphide and sulpho- 
cyanide of ammonia. 



^™ 



120 



THE STORY OF A PIECE OF COAL. 



Hitherto the purification of the gas has been 
brought about by mechanical means, but the gas 
now enters the "purifier" in which it undergoes 
a further cleansing, but this time by chemical 
means. The agent used is either lime or hydrated 




Fig. 37. 



oxide of iron, and by- their means the gas is 
robbed of its carbonic acid and the greater part 
of its sulphur compounds. The process is then 
considered complete, and the gas passes on into 
the water chamber over which the gas-holder is 
reared, and in which it rises through the water, 
forcing the huge cylinder upward according to 
the pressure it exerts. 

The gas-holder is poised between a number of 



HOW GAS IS MADE, ETC. 



121 



upright pillars by a series of chains and pulleys, 
which allow of its easy ascent or descent accord- 
ing as the supply is greater or less than that 
drawn from it by the gas mains. 

When we see the process which is necessary 
in order to obtain pure gas, we begin to appreci- 
ate to what an extent the atmosphere is fouled 
when many of the products of distillation, which, 
as far as the production of gas is concerned, may 



1 *k— 


^^^^^^^^W 


'- Cj I' - - — ~ Sj^ 


r~ *~ ~~/*^ : ~ : ^w^t^ 




WBiliii^iilta^ 


l^fiS i ^IpSSy 


EggBi 


fll^L^S^ rI-_ -Z "" «#^**'^^^^^^^^4 


ff^§Ss - : s^ - i v si " -iSKii 


55p^ 


*^^ pwlllilppr 


T— ^^^V 



Fig. 38. 



be called impurities, are allowed to escape free 
without let or hindrance. In these days of strict 
san ; tary inspection it seems strange that the air 
in the neighbourhood of gas-works is still al- 
lowed to become contaminated by the escape of 
impure compounds from the various portions of 
the gas-making apparatus. Go where one may, 
the presence of these compounds is at once ap- 
parent to the nostrils within a none too limited 
area around them, and yet their deleterious 



122 THE STORY OF A PIECE OF COAL. 

effects can be almost reduced to a minimum by 
the use of proper purifying agents, and by a 
scientific oversight of the whole apparatus. It 
certainly behoves all sanitary authorities to look 
well after any gas-works situated within their 
districts. 

Now let us see what these first five products 
of distillation actually are. 

Firstly, illuminating-gas. Everybody knows 
what this is. It cannot, however, be stated to be 
any one gas in particular, since it is a mechanical 
mixture of at least three different gases, and 
often contains small quantities of others. 

A very large proportion consists of what is 
known as marsh-gas, or light carburetted hydro- 
gen. This occurs occluded or locked up in the 
pores of the coal, and often oozes out into the 
galleries of coal-mines, where it is known as fire- 
damp (German damp/, vapour). It is disengaged 
wherever vegetable matter has fallen and has 
become decayed. If it were thence collected, 
together with an admixture of ten times its 
volume of air, a miniature coal-mine explosion 
could be produced by the introduction of a 
match into the mixture. Alone, however, it 
burns with a feebly luminous flame, although to 
its presence our house-gas owes a great portion 
of its heating power. Marsh-gas is the first of the 
series of hydrocarbons known chemically as the 
paraffins, and is an extremely light substance, 
being little more than half the weight of an 
equal bulk of air. It is composed of four atoms 
of hydrogen to one of carbon (CH 4 ). 

Marsh-gas, together with hydrogen and the 
monoxide of carbon, the last of which burns 
with a dull blue flame often seen at the surface 



HOW GAS IS MADE, ETC. 1 23 

of fires, particularly coke and charcoal fires, 
form about 87 per cent, of the whole volume of 
coal-gas, and are none of them anything but poor 
illuminants. 

The illuminating power of coal-gas depends 
on the presence therein of olefiant gas {ethylene), 
or, as it is sometimes termed, heavy carburetted 
hydrogen. This is the first of the series of 
hydro-carbons known as the defines, and is com- 
posed of two atoms of carbon to every four 
atoms of hydrogen (C 2 H 4 ). Others of the olefines 
are present in minute quantities. These assist 
in increasing the illuminosity, which is sometimes 
greatly enhanced, too, by the presence of a small 
quantity of benzene vapour. These illuminants, 
however, constitute but about 6 per cent, of the 
whole. 

Added to these, there are four other usual 
constituents which in no way increase the value 
of gas, but which rather detract from it. They 
are consequently as far as possible removed as 
impurities in the process of gas-making. These 
are nitrogen, carbonic acid gas, and the destruc- 
tive sulphur compounds, sulphuretted hydrogen 
and carbon bisulphide vapour. It is to the last 
two to which are to be attributed the injurious 
effects which the burning of gas has upon pictures, 
books, and also the tarnishing which metal fittings 
suffer where gas is burnt, since they give rise to 
the formation of oil of vitriol (sulphuric acid), 
which is being incessantly poured into the air. 
Of course the amount so given off is little as 
compared with that which escapes from a coal 
fire, but, fortunately for the inmates of the room, 
in this case the greater quantity goes up the 
chimney ; this, however, is but a method of post- 



124 THE STORY OF A PIECE OF COAL. 

poning the evil day, until the atmosphere becomes 
so laden with impurities that what proceeds at 
first up the chimney will finally again make its 
way back through the doors and windows. A 
recent official report tells us that, in the town 
of St. Helen's alone, sufficient sulphur escapes 
annually into the atmosphere to finally produce 
110,580 tons of sulphuric acid, and a computation 
has been made that every square mile of land in 
London is deluged annually with 180 tons of the 
same vegetation-denuding acid. It is a matter 
for wonder that any green thing continues to ex- 
ist in such places at all. 

The chief constituents of coal-gas are, there- 
fore, briefly as follows : — 

r (1) Hydrogen, 

(2) Marsh-gas (carburetted hydrogen or fire- 
damp), 

(3) Carbon monoxide, 

(4) Olefiant gas (ethylene, or heavy carbu- 
retted hydrogen), with other olefines, 

(5) Nitrogen, 

6) Carbonic acid gas, 

7) Sulphuretted hydrogen, 
(8) Carbon bisulphide (vapour), 

the last four being regarded as impurities, which 
are removed as far as possible in the manufac- 
ture. 

In the process of distillation of the coal, we 
have seen that various other important sub- 
stances are brought into existence. The final 
residue of coke, which is impregnated with the 
sulphur which has not been volatilised in the form 
flf sulphurous gases, we need scarcely more than 



HOW GAS IS MADE, ETC. 125 

mention here. But the gas-tar and the ammo- 
niacal liquor are two important products which 
demand something more than our casual atten- 
tion. At one time regarded by gas engineers as 
unfortunately necessary nuisances in the manu- 
facture of gas, they have both become so valuable 
on account of materials which can be obtained 
from them, that they enable gas itself to be sold 
now at less than half its original price. The 
waste of former generations is being utilised in 
this, and an instance is recorded in which tar, 
which was known to have been lying useless at the 
bottom of a canal for years, has been purchased by 
a gas engineer for distilling purposes. It has 
been estimated that about 590,000 tons of coal- 
tar are distilled annually. 

Tar in its primitive condition has been used, 
as every one is aware, for painting or tarring a 
variety of objects, such as barges and palings, in 
fact, as a kind of protection to the object covered 
from the ravages of insects and worms, or to pre- 
vent corrosion when applied to metal piers. But 
it is worthy of a better purpose, and is capable 
of yielding far more useful and interesting sub- 
stances than even the most imaginative individual 
could have dreamed of fifty years ago. 

In the process of distillation, the tar, after 
standing in tanks for some time, in order that 
any ammoniacal liquor which may be present 
may rise to the surface and be drawn off, is 
pumped into large stills, where a moderate amount 
of heat is applied to it. The result is that some 
of the more volatile products pass over and are 
collected in a receiver. These first products are 
known as first light oils, or crude coal-naphtha % and 
to this naphtha all the numerous natural naphthas 



T26 THE STORY OF A PIECE OF COAL. 

which have been discovered in various portions 
of the world, and to which have been applied 
numerous local names, bear a very close resem- 
blance. Such an one, for instance, was that small 
but famous spring at Riddings, in Derbyshire, 
from which the late Mr. Young — Paraffin Young 
— obtained his well-known paraffin oil, which gave 
the initial impetus to what has since developed 
into a trade of immense proportions in every 
quarter of the globe. 

After a time the crude coal-naphtha ceases to 
flow over, and the heat is increased. The result 
is that a fresh series of products, known as medium 
oils, passes over, and these oils are again collected 
and kept separate from the previous series. 
These in turn cease to flow, when, by a further 
increase of heat, what are known as the heavy 
oils finally pass over, and when the last of these, 
the "green grease," distils over, pitch alone is left 
in the still. Pitch is used to a large extent in the 
preparation of artificial asphalt, and also of a fuel 
known as " briquettes." 

The products thus obtained at the various 
stages of the process are themselves subjected 
to further distillation, and by the exercise of 
great care, requiring the most delicate and accu- 
rate treatment, a large variety of oils is obtained, 
and these are retailed under many and various 
fanciful names. 

One of the most important and best known 
products of the fractional distillation of crude 
coal-naphtha is that known as benzene, or benzole, 
(C 6 H 6 ). This, in its unrefined condition, is a light 
spirit which distils over at a point somewhat be- 
low the boiling point of water, but a delicate pro- 
cess of rectification is necessary to produce the 



HOW GAS IS MADE, ETC. 1 27 

pure spirit. Other products of the same light 
oils are toluene and xylene. 

Benzene of a certain quality is a very familiar 
and useful household article. In America light 
oils from petroleum are sold under this name. It 
is used for removing grease from clothing, clean- 
ing kid gloves, &c. If pure it is in reality a most 
dangerous spirit, being very inflammable; it is 
also extremely volatile, so much so that, if an un- 
corked bottle be left in a warm room where there 
is a fire or other light near, its vapour will prob- 
ably ignite. Should the vapour become mixed 
with air before ignition, it becomes a most dan- 
gerous explosive, and it will thus be seen how 
necessary it is to handle the article in household 
use in a most cautious manner. Being highly 
volatile, a considerable degree of cold is experi- 
enced if a drop be placed on the hand and allowed 
to evaporate. 

Benzene, which is only a compound of carbon 
and hydrogen, was first discovered by Faraday in 
1825 ; it is now obtained in large quantities from 
coal-tar, not so much for use as benzene as for 
its conversion, in the first place, by the action of 
nitric acid, into nitro -benzole, a liquid having an 
odour like the oil of bitter almonds, and which is 
much used by perfumers under the name of essence 
de mirbane; and, in the second place, for the pro- 
duction from this nitro-benzole of the far-famed 
aniline. After the distillation of benzene from the 
crude coal-naphtha is completed, the chief im- 
purities in the residue are charred and deposited 
by the action of strong sulphuric acid. By further 
distillation a lighter oil is given off, often known 
as artificial turpentine oil, which is used as a solvent 
for varnishes and lackers. This is very familiar 



128 THE STORY OF A PIECE OF COAL. 

to the costermonger of London as the oil which 
is burned in the flaring lamps which illuminate 
the New Cut or the Elephant and Castle on Satur- 
day and other market nights. 

By distillation of the heavy oils, carbolic acid 
and commercial anthracene are produced, and by a 
treatment of the residue, a white and crystalline 
substance known as naphthalin (C 10 H 8 ) is finally 
obtained. 

Thus, by the continued operation of the chem- 
ical process known as fractional distillation of the 
immediate products of coal-tar, these various 
series of useful oils are prepared. 

The treatment is much the same which has re- 
sulted in the production of paraffin oil, to which 
we have previously referred, and an account of 
the production of coal-oils would be very far from 
satisfactory, which made no mention of the pro- 
duction of similar commodities by the direct dis- 
tillation of shale. Oil-shales, or bituminous shales, 
exist in all parts of the world, and may be re- 
garded as mineral matter largely impregnated by 
the products of decaying vegetation. They there- 
fore greatly resemble some coals, and really only 
differ therefrom in degree, in the quantity of vege- 
table matter which they contain. Into .the sub- 
ject of the various native petroleums which have 
been found — for these rock-oils are better known 
as petroleums — in South America, in Burmah 
(Rangoon Oil), at Baku, and the shores of the 
Caspian, or in the United States of America, we 
need not enter, except to note that in all proba- 
bility the action of heat on underground bitumi- 
nous strata of enormous extent has been the cause 
of their production, just as on a smaller scale the 
action of artificial heat has forced the reluctant 



HOW GAS IS MADE, ETC. 1 29 

shale to give up its own burden of mineral oil. 
However, previous to 1847, although native min- 
eral oil had been for some years a recognised 
article of commerce, the causes which give rise to 
the oil-wells, and the source, probably a deep- 
seated one, oi the supply of oil, does not appear 
to have been well known, or at least was not en- 
quired after. But in that year Mr. Young, a 
chemist at Manchester, discovered that by distil- 
ling some petroleum, which he obtained from a 
spring at Riddings in Derbyshire, he was able to 
procure a light oil, which he used for burning in 
lamps, whilst the heavier product which he also 
obtained proved a most useful lubricant for ma- 
chinery. This naturally distilled oil was soon 
found to be similar to that oil which was noticed 
dripping from the roof of a coal-mine. Judging 
that the coal, being under the influence of heat, 
was the cause of the production of the oil, Mr. 
Young tested this conclusion by distilling the 
coal itself. Success attended his endeavour thus 
to procure the oil, and indelibly Young stamped 
his name upon the roll of famous men, whose in- 
dustrial inventions have done so much towards 
the accomplishment of the marvellous progress 
of the present century. From the distillation he 
obtained the well-known Young's Paraffin Oil, 
and the astonishing developments of the process 
which have taken place since he obtained his 
patent in 1850, for the manufacture of oils and 
solid paraffin, must have been a source of great 
satisfaction to him before his death, which oc- 
curred in 1883. 

Cannel coal, Boghead or Bathgate coal, and 
bituminous shales of various qualities, have all 
been requisitioned for the production of oils, and 

9 



130 THE STORY OF A PIECE OF COAL. 

from these various sources the crude naphthas, 
which bear a variety of names according to some 
peculiarity in their origin, or place of occur- 
rence, are obtained. Boghead coal, also known 
as "Torebanehill mineral/' gives Boghead naph- 
tha, while the crude naphtha obtained from shales 
is often quoted as shale-oil. In chemical com- 
position these naphthas are closely related to one 
another, and by fractional distillation of them 
similar series of products are obtained as those 
we have already seen as obtained from the crude 
coal-naphtha of coal-tar. 

In the direct distillation of cannel coal for 
the production of paraffin, it is necessary that the 
perpendicular tubes or retorts into which the coal 
is placed be heated only to a certain tempera- 
ture, which is considerably lower than that ap- 
plied when the object is the production of coal- 
gas. By this means nearly all the volatile matters 
pass over in the form of condensible vapours, and 
the crude oils are at once formed, from which 
are obtained at different temperatures various 
volatile ethers, benzene, and artificial turpentine 
oil or petroleum spirit. After these, safety-burn- 
ing paraffin oil, or kerosene, follows, but it is 
essential that the previous three volatile. products 
be completely cleared first, since, mixed with air, 
they form highly dangerous explosives. To the 
fact that the operation is carried on in the manu- 
factories with great care and accuracy can only 
be attributed the comparative rareness of explo- 
sions of the oil used in households. 

After paraffin, the heavy lubricating oils are 
next given off, still increasing the temperature, 
and, the residue being in turn subjected to a very 
low temperature, the white solid substance known 



HOW GAS IS MADE, ETC. 131 

as paraffin, so much used for making candles, is 
the result. By a different treatment of the same 
residue is produced that wonderful salve for ten- 
der skins, cuts, and burns, known popularly as 
vaseline. Probably no such widely-advertised 
remedial substance has so deserved its success as 
this universally used waste product of petroleum. 

We have noticed the fact that in order to pro- 
cure safety-burning oils, it is absolutely neces- 
sary that the more volatile portions be completely 
distilled over first. In most countries where these 
oils are much used a test is applied to them which 
consists in determining the flashing-point. Many 
of the more volatile ethers, which are highly in- 
flammable, are given off even at ordinary tem- 
peratures, and the application of a light to the 
oil will cause the volatile portion to " flash," as it 
is called. A safe kerosene, according to the laws 
of many of the United States, must not flash 
under ioo° Fahrenheit open test, and all those 
portions which flash at a less temperature must be 
volatilised off before the residue can be deemed a 
safe oil. It seems probable that the flashing- 
point will sooner or later be raised. 

One instance may be cited to show how neces- 
sary it is that the native mineral oils which have 
been discovered should have this effectual test 
applied to them. 

When the oil-wells were first discovered in 
America, the oil was obtained simply by a pro- 
cess of boring, and the fountain of oil which was 
bored into at times was so prolific, that it rushed 
out with a force which carried all obstacles before 
it, and defied all control. In one instance a col- 
umn of oil shot into the air to a height of forty 
feet, and defied all attempts to keep it under. In 



£32 THE STORY OF A PIECE OF COAL. 

order to prevent further accident, all lights in 
the immediate neighbourhood were extinguished, 
the nearest remaining being at a distance of four 
hundred feet. But in this crude naphtha there 
was, as usual, a quantity of volatile spirit which 
was being given off even at the temperature of 
the surrounding atmosphere. This soon became 
ignited, and with an explosion the column of oil 
was suddenly converted into a roaring column of 
fire. The owner of the property was thrown a 
distance of twenty feet by the explosion, and 
soon afterwards died from the burns which he 
had received from it. Such an accident could 
not now, however, happen. The tapping, stop- 
ping, and regulating of gushing wells can now be 
more effectually dealt with, and in the process of 
refining, the most inflammable portions are sepa- 
rated, with a result that, as the use of oil which 
flashes under ioo° F. open test is generally for- 
bidden, and as our normal temperature is con- 
siderably less than this, there is little to be feared 
in the way of explosion if the law be complied 
with. 

When the results of Mr. Young's labours be- 
came publicly known, a number of companies 
were started with the object of working on the 
lines laid down in his patent, and these not only 
in Great Britain but also in the United States, 
whither quantities of cannel coal were shipped 
from England and other parts to feed the retorts. 
In i860, according to the statistics furnished, 
some seventy factories were established in the 
United States alone with the object of extracting 
oil from coal and other mineral sources, such as 
bituminous shale, etc. When Young's patent 
finally expired, a still greater impetus was given 



HOW GAS IS MADE, ETC. 1 33 

to its production, and the manufacture would 
probably have continued to develop were it not 
that attention had, two years previously, been 
forcibly turned to those discoveries of great 
stores of natural oil in existence beneath a com- 
paratively thin crust of earth, and which, when 
bored into, spouted out to tremendous heights. 

The discovery of these oil-fountains entirely 
supplanted the industry in America and checked 
its development in England, but with the great pro- 
duction there has apparently been a greatly in- 
creased demand for it, and the British industry 
once again appears to thrive, until even bitumi- 
nous shales have been brought under requisition 
for their contribution to the national wealth. 

Were it not for the nuisance and difficulty 
experienced in the proper cleaning and trimming 
of lamps, there seems no other reason why min- 
eral oil should not in turn have superseded the 
use of gas, even as gas had, years before, super- 
seded the expensive animal and vegetable oils 
which had formerly been in use. 

Although this great development in the use of 
mineral oils has taken place only within the last 
thirty years, it must not be thought that their 
use is altogether of modern invention. That 
they were not altogether unknown in the fifth 
century before Christ is a matter of certainty, 
and at the time when the Persian Empire was at 
the zenith of its glory, the fires in the temples of 
the fire-worshippers were undoubtedly kept fed 
by the natural petroleum which the districts 
around afforded. It is thought by some that the 
legend which speaks of the fire which came down 
from heaven, and which lit the altars of the 
Zoroastrians, may have had its origin in the 



134 THE STORY OF A PIECE OF COAL. 

discovery of a hitherto unknown petroleum 
spring. More recently, the remarks of Marco 
Polo in his account of his travels in a. d. 1260 
and following years, are particularly interesting 
as showing that, even then, the use of mineral 
oil for various purposes was not altogether un- 
known. He says that on the north of Armenia 
the Greater is " Zorzania, in the confines of 
which a fountain is found, from which a liquor 
like oil flows, and though unprofitable for the 
seasoning of meat, yet is very fit for the supply- 
ing of lamps, and to anoint other things; and 
this natural oil flows constantly, and that in 
plenty enough to lade camels." 

From this we can infer that the nature of the 
oil was entirely unknown, for it was a "liquor 
like oil," and was also, strange to say, " unprofit- 
able for the seasoning of meat " ! In another 
place in Armenia, Marco Polo states that there 
was a fountain " whence rises oil in such abun- 
dance that a hundred ships might be at once 
loaded with it. It is not good for eating, but 
very fit for fuel, for anointing the camels in 
maladies of the skin, and for other purposes; 
for which reason people come from a great dis- 
tance for it, and nothing else is burned in all this 
country." 

The remedial effects of the oil, when used as 
an ointment, were thus early recognised, and the 
far-famed vaseline of the present day may be re- 
garded as the lineal descendant, so to speak, of 
the crude medicinal agent to which Marco Polo 
refers. 

The term asphalt has been applied to so many 
and various mixtures, that one scarcely associates 
it with natural mineral pitch which is found in 



HOW GAS IS MADE, ETC. 135 

some parts of the world. From time immemorial 
this compact, bituminous, resinous mineral has 
been discovered in masses on the shores of the 
Dead Sea, which has in consequence received the 
well-known title of Lake Asphaltites. Like the 
naphthas and petroleums which have been noticed, 
this has had its origin in the decomposition of 
vegetable matter, and appears to be thrown up 
in a liquid form by the volcanic energies which 
are still believed to be active in the centre of 
the lake, and which may be existent beneath a 
stratum, or bed, of oil-producing bitumen. 

In connection with the formation of this 
substance, the remarks of Sir Charles Lyell, 
the great geologist, may well be quoted as show- 
ing the transformation of vegetable matter into 
petroleum, and afterwards into solid-looking 
asphalt. At Trinidad is a lake of bitumen 
which is a mile and a half in circumference. 
" The Orinoco has for ages been rolling down 
great quantities of woody and vegetable bodies 
into the surrounding sea, where, by the influence 
of currents and eddies, they may be arrested, and 
accumulated in particular places. The frequent 
occurrence of earthquakes and other indications 
of volcanic action in those parts, lend counte- 
nance to the opinion that these vegetable sub- 
stances may have undergone, by the agency 
of subterranean fire, those transformations or 
chemical changes which produce petroleum; and 
this may, by the same causes, be forced up to the 
surface, where, by exposure to the air, it becomes 
inspissated, and forms those different varieties 
of earth-pitch or asphaltum so abundant in the 
island." 

It is interesting to note also that it was ob- 



136 THE STORY OF A PIECE OF COAL. 

tained, at an ancient period, from the oil-fountains 
of Is, and that it was put to considerable use in 
the embalming of the bodies of the Egyptians. It 
appears, too, to have been employed in the con- 
struction of the walls of Babylon, and thus from 
very early times these wonderful products and 
results of decayed vegetation have been brought 
into use for the service of man. 

Aniline has been previously referred to (p. 127) 
as having been prepared from nitro-benzole, or 
essence de mirbane, and its preparation, by treating 
this substance with iron-filings and acetic acid, 
was one of the early triumphs of the chemists 
who undertook the search after the unknown 
contained in gas-tar. It had previously been ob- 
tained from oils distilled from bones. The 
importance of the substance lies in the fact 
that, by the action of various chemical reagents, 
a series of colouring matters of very great rich- 
ness are formed, and these are the well-known 
aniline dyes. 

As early as 1836, it was discovered that ani- 
line, when heated with chloride of lime, acquired 
a beautiful blue tint. This discovery led to no 
immediate practical result, and it was not until 
twenty-one years after that a further discovery 
was made, which may indeed be said to have 
achieved a world-wide reputation. It was found 
that, by adding bichromate of potash to a solution 
of aniline and sulphuric acid, a powder was ob- 
tained from which the dye was afterwards ex- 
tracted, which is known as mauve. Since that 
time dyes in all shades and colours have been 
obtained from the same source. Magenta was 
the next dye to make its appearance, and in the 
fickle history of fashion, probably no colours 



HOW GAS IS MADE, ETC. 137 

had such extraordinary runs of popularity as 
those of mauve and magenta. Every conceivable 
colour was obtained in due course from the same 
source, and chemists began to suspect that, in the 
course of time, the colouring matter of dyer's 
madder, which was known as alizarin, would 
also be obtained therefrom. Hitherto this had 
been obtained from the root of the madder-plant, 
but by dint of careful and well-reasoned research, 
it was obtained by Dr. Groebe, from a solid 
crystalline coal-tar product, known as anthracene, 
(C 12 H 14 ). This artificial alizarin yields colours 
which are purer than those of natural madder, 
and being derived from what was originally re- 
garded as a waste product, its cost of production 
is considerably cheaper. 

We have endeavoured thus far to deal with 
(1) gas, and (2) tar, the two principal products 
in the distillation of coal. We have yet to say 
a few words concerning the useful ammoniacai 
liquor, and the final residue in the retorts, i.e., 
coke. 

The ammoniacai liquor which has been pass- 
ing over during distillation of the coal, and which 
has been collecting in the hydraulic main and in 
other parts of the gas-making apparatus, is set 
aside to be treated to a variety of chemical re- 
actions, in order to wrench from it its useful con- 
stituents. Amongst these, of course, ammonia 
stands in the first rank, the others being compar- 
atively unimportant. In order to obtain this, the 
liquor is first of all neutralised by being treated 
with a quantity of acid, which converts the prin- 
cipal constituent of the liquor, viz., carbonate 
of ammonia (smelling salts), into either sulphate 
of ammonia, or chloride of ammonia, familiarly 



138 THE STORY OF A PIECE OF COAL. 

known as sal-ammoniac, according as sulphuric 
acid or hydrochloric acid is the acid used. Thus 
carbonate of ammonia with sulphuric acid will give 
sulphate of ammonia, but carbonate of ammonia 
with hydrochloric acid will give sal-ammoniac 
(chloride of ammonia). By a further treatment 
of these with lime, or, as it is chemically known, 
oxide of calcium, ammonia is set free, whilst 
chloride of lime (the well-known disinfectant), or 
sulphate of lime (gypsum, or " plaster of Paris "), 
is the result. 
Thus: 

Sulphate of ammonia + lime = plaster of Paris + ammonia, 
or, 
Sal-ammoniac + lime = chloride of lime 4- ammonia. 

\mmonia itself is a most powerful gas, and 
acts rapidly upon the eyes. It has a stimulating 
effect upon the nerves. It is not a chemical ele- 
ment, being composed of three parts of hydrogen 
by weight to one of nitrogen, both of which ele- 
ments alone are very harmless, and the latter, 
indeed, very necessary to human life. Ammonia 
is fatal to life, producing great irritation of the 
lungs. 

It has also been called " hartshorn, " being 
obtained by destructive distillation of horn and 
bone. The name u ammonia " is said to have 
been derived from the fact that it w T as first ob- 
tained by the Arabs near the temple of Jupiter 
Ammon, in Lybia, North Africa, from the ex- 
crement of camels, in the form of sal-ammoniac. 
There are always traces of it in the atmosphere, 
especially in the vicinity of large towns and 
manufactories where large quantities of coal are 
burned. 



HOW GAS IS MADE, ETC. 1 39 

Coke, if properly prepared, should consist of 
pure carbon. Good coal should yield as much as 
80 per cent, of coke, but owing to the unsatisfac- 
tory manner of its production, this proportion is 
seldom yielded. The coke which is left in the 
retorts after gas-making is sold to bakeries, 
laundries, factories, and also for household pur- 
poses. It kindles easily and burns rapidly, hence 
it is especially useful when a quick hot fire is 
wanted, and it is also employed to aid the burn- 
ing of hard coal. Naturally a coke fire must be 
replenished oftener than one of coal. In the 
household it is said that owing to the quantity of 
oxygen required in its combustion, it gives rise to 
feelings of suffocation where insufficient ventila- 
tion of the room is provided. 

Large quantities of coke are, however, con- 
sumed in the feeding of furnace fires, and in the 
heating of boilers of locomotives, as well as in 
metallurgical operations; and in order to supply 
the demand, large quantities of coal are " coked/* 
a process by which the volatile products are com- 
pletely burnt off, pure coke remaining behind. 
This process is therefore the direct opposite to 
that of " distillation, " by which the volatile prod- 
ducts are carefully collected and re-distilled. 

The sulphurous impurities which occur in 
most bituminous coals, and which are, to a certain 
extent, retained in coke made at the gas-works, 
themselves have a value, which in these utilitarian 
days is not long likely to escape the attention of 
capitalists. In coal, bands of bright shining iron 
pyrites are frequently seen, even in the homely 
scuttle, and when coal is washed, as it is in some 
places, the removal of the pyrites increases the 
value of the coal, whilst it has a value of its own. 



140 THE STORY OF A PIECE OF COAL. 

The conversion of the sulphur contained in 
pyritic coal first into the very offensive gas, sul- 
phuretted hydrogen, and then into sulphuric acid, 
has been referred to, and it is to be hoped that in 
these days when every available source of wealth 
is being looked up, and when there threatens to 
remain nothing which shall in the future be known 
as " waste," that the atmosphere will be spared 
being longer the receptacle for the unowned and 
execrated brimstone of millions of fires and fur- 
naces. 



CHAPTER VII. 

THE COAL SUPPLIES OF THE WORLD. 

As compared with some of the American coal- 
fields, those of Britain are but small, both in ex- 
tent and thickness. They can be regarded as 
falling naturally into three principal areas. 

The northern coal-field, including those of 
Fife, Stirling, and Ayr in Scotland ; Cumber- 
land, Newcastle, and Durham in England; 
Tyrone in Ireland. 

The middle coal-field, all geologically in 
union, including those of Yorkshire, Derby- 
shire, Shropshire, Staffordshire, Flint, and 
Denbigh. 

The southern coal-field, including South Wales, 
Forest of Dean, Bristol, Dover, with an off- 
shoot at Leinster, &c., and Millstreet, Cork. 

Thus it will be seen that while England and 
Scotland are, in comparison with their extent of 



THE COAL SUPPLIES OF THE WORLD. 141 

surface, bountifully supplied with coal-areas, in 
the sister island of Ireland coal-producing areas 
are almost absent. The isolated beds in Cork 
and Tipperary, in Tyrone and Antrim, are but 
the remnants left of what were formerly beds of 
coal extending the whole breadth and length of 
Ireland. Such beds as there remain undoubtedly 
belong to the base of the coal-measures, and 
observations all go to show that the surface 
suffered such extreme denudation subsequent to 
the growth of the coal-forests, that the wealth 
which orice lay there, has been swept away from 
the surface which formerly boasted of it. 

On the continent of Europe the coal-fields, 
though not occupying so large a proportion of 
the surface of the country as in England, are 
very far from being slight or to be disregarded. 
The extent of forest-lands still remaining in Ger- 
many and Austria are sufficing for the immediate 
needs of the districts where some of the best 
seams occur. It is only where there is a dearth 
of handy fuel, ready to be had, perhaps, by the 
simple felling of a few trees, that man commences 
to dig into the earth for his fuel. But although 
on the continent not yet occupying so prominent 
a position in public estimation as do coal-fields 
in Great Britain, those of the former have one 
conspicuous characteristic, viz., the great thick- 
ness of some of the individual seams. 

In the coal-field of Midlothian the seams of 
coal vary from 2 feet to 5 feet in thickness. 
One of them is known as the " great seam," and 
in spite of its name attains a thickness only of 
from 8 to 10 feet thick. There are altogether 
about thirty seams of coal. When, however, we 
pass to the continent, we find many instances, 



142 THE STORY OF A PIECE OF COAL. 

such as that of the coal-field of Central France, 
in which the seams attain vast thicknesses, many 
of them actually reaching 40 and 60 feet, and 
sometimes even 80 feet. One of the seams in the 
district of St. Etienne varies from 30 to 70 feet 
thick, whilst the fifteen to eighteen workable 
seams give a thickness of 112 feet, although the 
total area of the field is not great. Again, in the 
remarkable basin of the Saone-et-Loire, although 
there are but ten beds of coal, two of them run 
from 30 to 60 feet each, whilst at Creusot the 
main seam actually runs locally to a thickness 
varying between 40 and 130 feet. 

The Belgian coal-field stretches in the form of 
a narrow strip from 7 to 9 miles wide by about 
100 miles long, and is divided into three prin- 
cipal basins. In that stretching from Liege to 
Verviers there are eighty-three seams of coal, 
none of which are less than 3 feet thick. In the 
basin of the Sambre, stretching from Namur to 
Charleroi, there are seventy-three seams which 
are workable, whilst in that between Mons and 
Thulin there are no less than one hundred and 
fifty-seven seams. The measures here are so 
folded in zigzag fashion, that in boring in the 
neighbourhood of Mons to a depth of 350 yards 
vertical, a single seam was passed through no 
less than six times. 

Germany, on the west side of the Rhine, is 
exceptionally fortunate in the possession of the 
famous Pfalz-Saarbrlicken coal-field, measuring 
about 60 miles long by 20 miles wide, and cover- 
ing about 175 square miles. Much of the coal 
which lies deep in these coal-measures will always 
remain unattainable, owing to the enormous 
thickness of the strata, but a careful computation 



THE COAL SUPPLIES OF THE WORLD. 143 

made of the coal which can be worked, gives an 
estimate of no less than 2750 millions of tons. 
There is a grand total of two hundred and forty- 
four seams, although about half of them are un- 
workable. 

Beside other smaller coal-producing areas in 
Germany, the coal-fields of Silesia in the south- 
eastern corner of Prussia are a possession un- 
rivalled both on account of their extent and 
thickness. It is stated that there exist 333 feet 
of coal, all the seams of which exceed 2-J- feet, 
and that in the aggregate there is here, within a 
workable depth, the scarcely conceivable quantity 
of 50,000 million tons of coal. 

The coal-field of Upper Silesia, occupying an 
area about 20 miles long by 15 miles broad, is 
estimated to contain some 10,000 feet of strata, 
with 333 feet of good coal. This is about three 
times the thickness contained in the South Wales 
coal-field, in a similiar thickness of coal-measures. 
There are single seams up to 60 feet thick, but 
much of the coal is covered by more recent rocks 
of New Red and Cretaceous age. In Lower 
Silesia there are numerous seams 3I feet to 5 feet 
thick, but owing to their liability to change in 
character even in the same seam, their value is 
inferior to the coals of Upper Silesia. 

When British supplies are at length exhausted, 
it is anticipated that some of the earliest coals to 
be imported, should coal then be needed, will 
reach Britain from the upper waters of the Oder. 

The coal-field of Westphalia has lately come 
into prominence in connection with the search 
which has been made for coal in Kent and Surrey, 
the strata which are mined at Dortmund being 
thought to be continuous from the Bristol coal- 



144 THE STORY OF A PIECE OF COAL. 

field. Borings have been made through the chalk 
of the district north of the Westphalian coal-field, 
and these have shown the existence of further 
coal-measures. The coal-fields extends between 
Essen and Dortmund a distance of 30 miles east 
and west, and exhibits a series of about one hun- 
dred and thirty seams, with an aggregate of 300 
feet of coal. 

It is estimated that this coal-field alone con- 
tains no less than 39,200 millions of tons of coal. 

Russia possesses supplies of coal whose in- 
fluence has scarcely yet been felt, owing to the 
sparseness of the population and the abundance 
of forest. Carboniferous rocks abut against the 
flanks of the Ural Mountains, along the sides of 
which they extend for a length of about a thou- 
sand miles, with inter-stratifications of coal. 
Their actual contents have not yet been gauged, 
but there is every reason to believe that those 
coal-beds which have been seen are but samples 
of many others which will, when properly worked, 
satisfy the needs of a much larger population than 
the country now possesses. 

Like the lower coals of Scotland, the Russian 
coals are found in the carboniferous limestone. 
This may also be said of the coal-fields in the 
governments of Tula and Kaluga, and of those im- 
portant coal-bearing strata near the river Donetz, 
stretching to the northern corner of the Sea of 
Azov. In the last-named the seams are spread 
over an area of 11,000 square miles, in which 
there are forty-four workable seams containing 
114 feet of coal. The thickest of known Rus- 
sian coals occur at Lithwinsk, where three seams 
are worked, each measuring 30 feet to 40 feet 
thick. 



THE COAL SUPPLIES OF THE WORLD. 145 

An extension of the Upper Silesian coal-field 
appears in Russian Poland. This is of upper 
Carboniferous age, and contains an aggregate of 
60 feet of coal. 

At Ostrau, in Upper Silesia (Austria), there is 
a remarkable coal-field. Of its 370 seams there 
are no less than 117 workable ones, and these 
contain 350 feet of coal The coals here are very 
full of gas, which even percolates to the cellars of 
houses in the town. A bore hole which was sunk 
in 1852 to a depth of 150 feet, gave off a stream 
of gas, which ignited, and burnt for many years 
with a flame some feet long. 

The Zwickau coal-field in Saxony is one of 
the most important in Europe. It contains a re- 
markable seam of coal, known as Russokohle or 
soot-coal, running at times 25 feet thick. It was 
separated by Geinitz and others into four zones, 
according to their vegetable contents, viz. : — 

1. Zone of Ferns. 

2. Zone of Annularia and Calamites. 

3. Zone of Sigillaria. 

4. Zone of Sagenaria (in Silesia), equivalent 

to the culm-measures of Devonshire. 

Coals belonging to other than true Carbon- 
iferous age are found in Europe at Steyerdorf on 
the Danube, where there are a few seams of good 
coal in strata of Liassic age, and in Hungary and 
Styria, where there are tertiary coals which ap- 
proach closely to those of true Carboniferous age 
in composition and quality. 

In Spain there are a few small scattered ba- 
sins. Coal is found overlying the carboniferous 
limestone of the Cantabrian chain, the seams 
10 



146 THE STORY OF A PIECE OF COAL. 

being from 5 feet to 8 feet thick. In the Satero- 
valley, near Sotillo, is a single seam measuring 
froni 60 feet to 100 feet thick. Coal of Neoco- 
mian age appears at Montalban. 

When we look outside the continent of Eu- 
rope, we may well be astonished at the bountiful 
manner in which nature has laid out beds of coal 
upon these ancient surfaces of our globe. 

Professor Rogers estimated that, in the United 
States of America, the coal-fields occupy an area 
of no less than 196,850 square miles. 

Here, again, it is extremely probable that the 
coal-fields which remain, in spite of their gigantic 
existing areas, are but the remnants of one tre- 
mendous area of deposit, bounded only on the 
east by the Atlantic, and on the west by a line 
running from the great lakes to the frontiers 
of Mexico. The whole area has been subjected 
to forces which have produced foldings and 
flexures in the Carboniferous strata after depo- 
sition. These undulations are greatest near the 
Alleghanies, and between these mountains and the 
Atlantic, whilst the flexures gradually dying out 
westward, cause the strata there to remain fairly 
horizontal. In the troughs of the foldings thus 
formed the coal-measures rest, those portions 
which had been thrown up as anticlines having 
suffered loss by denudation. Where the foldings 
are greatest there the coal has been naturally 
most altered ; bituminous and caking-coals are 
characteristic of the broad flat areas west of the 
mountains, whilst, where the contortions are 
greatest, the coal becomes a pure anthracite. 

It must not be thought that in this huge area 
the coal is all uniformly good. It varies greatly 
in quality, and in some districts it occurs in such 



THE COAL SUPPLIES OF THE WORLD. I4 y 

thin seams as to be worthless, except as fuel for 
consumption by the actual coal-getters. There 
are, too, areas of many square miles in extent, 
where there are now no coals at all, the forma- 
tion having been denuded right down to the 
palaeozoic back-bone of the country. 

The chief of the actual coal-fields is that of 
Pennsylvania. The output of anthracite here ex- 
ceeds that of bituminous coal, and it is estimated 
that the supply will last between ioo and 150 
years longer. The great field of which this is a 
portion, extends in an unbroken length for 875 
miles N. E. and S. W., and includes the basins of 
Ohio, Maryland, Virginia, Kentucky, and Tennes- 
see. The workiable seams of anthracite about 
Pottsville measure in the aggregate from 70 to 
207 feet. Some of the lower seams individually 
attain an exceptional thickness, that at Lehigh 
Summit mine containing a seam, or rather a bed, 
of 30 feet of good coal. 

The remarkable Pittsburg Seam of bituminous 
coal is 8 feet thick at its outcrop near the city of 
Pittsburg, whence it takes its name, and although 
its thickness varies considerably, Professor Rogers 
estimated that the sheet of coal measures super- 
ficially about 14,000 square miles. What a forest 
there must have existed to produce so widespread 
a bed! Even as it is, it has at a former epoch 
suffered great denudation, if certain detached 
basins should be considered as indicating its for- 
mer extent, 

The principal seam in the anthracite district 
of central Pennsylvania, which extends for about 
650 miles along the left bank of the Susque- 
hanna, is known as the " Mammoth " vein, and 
is 29J feet thick at Wilkesbarre, whilst at 



148 THE STORY OF A PIECE OF COAL. 

other places it attains to, and even exceeds, 60 
feet. 

On the west of the chain of mountains the 
foldings become gentler, and the coal assumes an 
almost horizontal position. In passing through 
Ohio we find a saddle-back ridge or anticline of 
more ancient strata than the coal, and in con- 
sequence of this, we have a physical boundary 
placed upon the coal-fields on each side. 

Passing across this older ridge of denuded 
Silurian and other rocks, we reach the famous Illi- 
nois and Indiana coal-field, whose coal-measures 
lie in a broad trough, bounded on the west by 
the uprising of the carboniferous limestone of 
the Upper Mississippi. This limestone forma- 
tion appears here for the first time, having been 
absent on the eastern side of the Ohio anticline. 
The area of the coal-field is estimated at 51,000 
square miles. 

In connection with the coal-fields of the United 
States, it is interesting to notice that a wide area 
in Texas, estimated at 3000 square miles, pro- 
duces a large amount of coal annually from 
strata of the Liassic age. Another important area 
of production in eastern Virginia contains coal 
referable to the Jurassic age, and is similar in 
fossil contents to the Jurassic of Whitby and 
Brora. The main seam in eastern Virginia 
boasts a thickness of from 30 to 40 feet of good 
coal. 

Very serviceable lignites of Cretaceous age 
are found on the Pacific slope, to which age those 
of Vancouver's Island and Saskatchewan River 
are referable. 

Other coal-fields of less importance are found 
between Lakes Huron and Erie, where the meas- 



THE COAL SUPPLIES OF THE WORLD. 149 

ures cover an area of 5000 square miles, and also 
in Rhode Island. 

In British North America we find extensive 
deposits of valuable coal-measures. Large de- 
velopments occur in New Brunswick and Nova 
Scotia. At South Joggins there is a thickness of 
14,750 feet of strata, in which are found seventy- 
six coal-seams of 45 feet in total thickness. At 
Pictou there are six seams with a total of 80 feet 
of coal. In the lower carboniferous group is 
found the peculiar asphaltic coal of the Albert 
mine in New Brunswick. Extensive deposits of 
lignite are met with both in the Dominion and in 
the United States, whilst true coal-measures 
flank both sides of the Rocky Mountains. Coal- 
seams are often encountered in the Arctic archi- 
pelago. 

The principal areas of deposit in South Ameri- 
ca are in Brazil, Uruguay, and Peru. The largest 
is the Candiota coal-field, in Brazil, where sec- 
tions in the valley of the Candiota River show 
five good seams with a total of 65 feet of coal. 
It is, however, worked but little, the principal 
workings being at San Jeronimo on the Jacaha- 
hay River. 

In Peru the true carboniferous coal-seams are 
found on the higher ground of the Andes, whilst 
coal of secondary age is found in considerable 
quantities on the rise towards the mountains. 
At Porton, east of Truxillo, the same meta- 
morphism which has changed the ridge of sand- 
stone to a hard quartzite has also changed the 
ordinary bituminous coal into an anthracite, 
which is here vertical in position. The coals of 
Peru usually rise to more than 10,000 feet above 
the sea, and they are practically inaccessible. 



150 THE STORY OF A PIECE OF COAL. 

Cretaceous coals have been found at Lota in 
Chili, and at Sandy Point, Straits of Magellan. 

Turning to Asia, we find that coal has been 
worked from time to time at Heraclea in Asia 
Minor. Lignites are met with at Smyrna and 
Lebanon. 

The coal-fields of Hindustan are small but 
numerous, being found in all parts of the penin- 
sula. There is an important coal-field at Rani- 
ganj, near the Hooghly, 140 miles north of Cal- 
cutta. It has an area of 500 square miles. In 
the Raniganj district there are occasional seems 
20 feet to 80 feet in thickness, but the coals are 
of somewhat inferior quality. 

The best quality amongst Indian coals has 
come from a small coal-field of about n square 
miles in extent, situated at Kurhurbali on the 
East Indian Railway. Other coal-fields are found 
at Jherria and on the Sone River, in Bengal, and 
at Mopani on the Nerbudda. Much is expected 
in future from, the large coal-field of the Wardha 
and Chanda districts, in the Central Provinces, 
the coal of which may eventually prove to be of 
Permian age. 

The coal-deposits of China are undoubtedly 
of tremendous extent, although from want of ex- 
ploration it is difficult to form any satisfactory 
estimate of them. Near Pekin there are beds of 
coal 95 feet thick, which afford ample provision 
for the needs of the city. In the mountainous 
districts of western China the area over which 
carboniferous strata are exposed has been esti- 
mated at 100,000 square miles. The coal-measures 
extend westward to the Mongolian frontier, 
where coal-seams 30 feet thick are known to lie 
in horizontal plane for 200 miles. Most of the 



THE COAL SUPPLIES OF THE WORLD. 151 

Chinese coal-deposits are rendered of small value, 
either owing to the mountainous nature of the 
valleys in which they outcrop, or to their inac- 
cessibility from the sea. Japan is not lacking in 
good supplies of coal. A colliery is worked by 
the government on the island of Takasima, near 
Nagasaki, for the supply of coals for the use of 
the navy. 

The British possession of Labuan, off the island 
of Borneo, is rich in a coal of tertiary age, remark- 
able for the quantity of fossil resin which it con- 
tains. Coal' is also found in Sumatra, and in the 
Malayan Archipelago. 

In Cape Colony and Natal the coal-bearing 
Karoo beds are probably of New Red age. The 
coal is reported to be excellent in quantity. 

In Abyssinia lignites are frequently met with 
in the high lands of the interior. 

Coal is very extensively developed throughout 
Australasia. In New South Wales, coal-measures 
occur in large detached portions between 29 and 
35 S. latitude. The Newcastle district, at the 
mouth of the Hunter river, is the chief seat of 
the coal trade, and the seams are here found up 
to 30 feet thick. Coal-bearing strata are found 
at Rowen River, in Queensland, covering an area 
of 24,000 square miles, whilst important mines of 
Cretaceous age are worked at Ipswich, near Bris- 
bane. In New Zealand quantities of lignite, de- 
scribed as a hydrous coal, are found and utilised ; 
also an anhydrous coal which may prove to be 
either of Cretaceous or Jurassic age. 

We have thus briefly sketched the supplies of 
coal, so far as they are known, which are to be 
found in various countries. But England has of 
late years been concerned as to the possible fail- 



T52 THE STORY OF A PIECE OF COAL. 

lire, of her home supplies in the not very distant 
future, and the effects which such failure would 
be likely to produce on the commercial prosperity 
of the country. 

Great Britain has long been the centre of the 
universe in the supply of the world's coal, and as 
a matter of fact, has been for many years raising 
considerably more than one half of the total 
amount of coal raised throughout the whole 
world. There is, as we have seen, an abundance 
of coal elsewhere, which will, in the course of 
time, compete with her when properly worked, 
but Britain seems to have early taken the lead in 
the production of coal, and to have become the 
great universal coal distributor. Those who have 
misgivings as to what will happen when her coal 
is exhausted, receive little comfort from the fact 
that in North America, in Prussia, in China and 
elsewhere, there are tremendous supplies of coal 
as yet untouched, although a certain sense of re- 
lief is experienced when that fact becomes gener- 
ally known. 

If by the time of exhaustion of the home 
mines Britain is still dependent upon coal for 
fuel, which, in this age of electricity, scarcely 
■seems probable, her trade and commerce will feel 
with tremendous effect the blow which her pres- 
tige will experience when the first vessel, laden 
with foreign coal, weighs anchor in a British har- 
bour. In the great coal lock-out of 1893, when, 
for the greater part of sixteen weeks, scarcely a 
ton of coal reached the surface in some of her 
principal coal-fields, it was rumoured, falsely as 
it appeared, that a collier from America had in- 
deed reached those shores, and the importance 
which attached to the supposed event was shown 



THE COAL SUPPLIES OF THE WORLD. 153 

by the anxious references to it in the public press, 
where the truth or otherwise of the alarm was 
actively discussed. Should such a thing at any 
time actually come to pass, it will indeed be a 
retribution to those who have for years been 
squandering their inheritance in many a wasteful 
manner of coal-consumption. 

Thirty years ago, when so much small coal 
was wasted and wantonly consumed in order to 
dispose of it in the easiest manner possible at the 
pit-mouths, and when only the best and largest 
coal was deemed to be of any value, louder and 
louder did scientific men speak in protest against 
this great and increasing prodigality. Wild esti- 
mates were set on foot showing how that, sooner 
or later, there would be in Britain no native sup- 
ply of coal at all, and finally a Royal Commission 
was appointed in 1866, to collect evidence and 
report upon the probable time during which the 
supplies of Great Britain would last. 

This Commission reported in 187 1, and the 
outcome of it was that a period of twelve hun- 
dred and seventy-three years was assigned as the 
period during which the coal would last, at the 
then-existing rate of consumption. The quantity 
of workable coal within a depth of 4000 feet wa? 
estimated to be 90,207 millions of tons, or, in- 
cluding that at greater depths, 146,480 millions 
of tons. Since that date, however, there has been 
a steady annual increase in the amount of coal 
consumed, and subsequent estimates go to show 
that the supplies cannot last for more than 250 
years, or, taking into consideration a possible 
decrease in consumption, 350 years. Most of the 
coal-mines will, indeed, have been worked out in 
less than a hundred years hence, and then, per- 



154 TH E STORY OF A PIECE OF COAL. 

haps, the competition brought about by the de- 
mand for, and the scarcity of, coal from the re- 
maining mines, will have resulted in the dreaded 
importation of coal from abroad. 

In referring to the outcome of the Royal 
Commission of 1866, although the Commissioners 
fixed so comparatively short a period as the 
probable duration of the coal supplies, it is but 
fair that it should be stated that other estimates 
have been made which have materially differed 
from their estimate. Whereas one estimate more 
than doubled that of the Royal Commission, that 
of Sir William Armstrong in 1863 gave it as 212 
years, and Professor Jevons, speaking in 1875 
concerning Armstrong's estimate, observed that 
the annual increase in the amount used, which 
was allowed for in the estimate, had so greatly 
itself increased, that the 212 years must be con- 
siderably reduced. 

One can scarcely thoroughly appreciate the 
enormous quantity of coal that is brought to the 
surface annually, and the only wonder is that 
there are any supplies left at all. The Great 
Pyramid, which is said by Herodotus to have 
been twenty years in building, and which took 
100,000 men to build, contains 3,394,307 cubic 
yards of stone. The coal raised in 1892 "would 
make a pyramid which would contain 181,500,000 
cubic yards, at the low estimate that one ton 
could be squeezed into one cubic yard. 

The increase in the quantity of coal which has 
been raised in succeeding years can well be seen 
from the following facts. 

In 1820 there were raised in Great Britain 
about 20 millions of tons. By 1855 this amount 
had increased to 64!- millions. In 1865 this again 



THE COAL-TAR COLOURS. 1 55 

had increased to 98 millions, whilst twenty years 
after, viz., in 1885, this had increased to no less 
than 159 millions, such were the giant strides 
which the increase in consumption made. 

In the return for 1892, this amount had farther 
increased to i8i|- millions of tons, an advance in 
eight years of a quantity more than equal to the 
total raised in 1820, and in 1894 the total reached 
199^ millions; this was produced by 795,240 per- 
sons, employed in and about the mines. 



CHAPTER VIII. 

THE COAL-TAR COLOURS. 

In a former chapter some slight reference has 
been made to those bye-products of coal-tar which 
have proved so valuable in the production of the 
aniline dyes. It is thought that the subject is of 
so interesting a nature as to deserve more notice 
than it was possible to bestow upon it in that 
place. With abstruse chemical formulae and com- 
plex chemical equations it is proposed to have as 
little as possible to do, but even the most unscien- 
tific treatment of the subject must occasionally 
necessitate a scientific method of elucidation. 

The dyeing industry has been radically changed 
during the last half century by the introduction of 
what are known as the artificial dyes, whilst the 
natural colouring matters which had previously 
been the sole basis of the industry, and which had 
been obtained by very simple chemical methods 
from some of the constituents of the animal king- 
dom, or which were found in a natural state in 



156 THE STORY OF A PIECE OF COAL. 

the vegetable kingdom, have very largely given 
place to those which have been obtained from 
coal-tar, a product of the mineralised vegetation 
of the carboniferous age. 

The development and discovery of the aniline 
colouring matters were not, of course, possible 
until after the extensive adoption of house-gas 
for illuminating purposes, and even then it was 
many years before the waste products from the 
gas-works came to have an appreciable value of 
their own. This, however, came with the in- 
creased utilitarianism of the commerce of the 
present century, but although aniline was first 
discovered in 1826 by Unverdorben, in the 
materials produced by the dry distillation of 
indigo (Portuguese, anil, indigo), it was not un- 
til thirty years afterwards, namely, in 1856, that 
the discovery of the method of manufacture of 
the first aniline dye, mauveine, was announced, 
the discovery being due to the persistent efforts 
of Perkin, to whom, together with other chemists 
working in the same field, is due the great ad- 
vance which has been made in the chemical 
knowledge of the carbon, hydrogen, and oxygen 
compounds. Scientists appeared to work along 
two planes ; there were those who discovered 
certain chemical compounds in the resulting pro- 
ducts of reactions in the treatment of existing 
vegetation, and there were those who, studying 
the wonderful constituents in coal-tar, the pro- 
duct of a past age, immediately set to work to 
find therein those compounds which their con- 
temporaries had already discovered. Generally, 
too, with signal success. 

The discovery of benzene in 1825 by Faraday 
was followed in the course of a few years by its 



THE COAL-TAR COLOURS. 



157 



discovery in coal-tar by Hofmann. Toluene, 
which was discovered in 1837 by Pelletier, was 
recognised in the fractional distillation of crude 
naphtha by Mansfield in 1848. Although the 
method of production of mauveine on a large 
scale was not accomplished until 1856, yet it had 
been noticed in 1834, the actual year of its recog- 
nition as a constituent of coal-tar, that, when 
Brought into contact with chloride of lime, it 
gave brilliant colours, but it required a consider- 
able cheapening of the process of aniline manu- 
facture before the dyes commenced to enter into 
competition with the old natural dyes. 

The isolation of aniline from coal-tar is ex- 
pensive, in consequence of the small quantities in 
which it is there found, but it was discovered by 
Mitscherlich that by acting upon benzene, one of 
the early distillates of coal-tar, for the production 
•of nitrobenzole, a compound was produced from 
which aniline could be obtained in large quanti- 
ties. There were thus two methods of obtain- 
ing aniline from tar, the experimental and the 
practical. 

In producing nitrobenzole (nitrobenzene), 
chemically represented as C 6 H 5 N0 3 , the nitric 
acid used as the reagent with benzene, is mixed 
with a quantity of sulphuric acid, with the object 
of absorbing water which is formed during the 
reaction, as this would tend to dilute the efficien- 
cy of the nitric acid. The proportions are 100 
parts of purified benzene, with a mixture of 115 
parts of concentrated nitric acid (HN0 3 ), and 
160 parts of concentrated sulphuric acid. The 
mixture is gradually introduced into the large 
cast-iron cylinder into which the benzene has been 
poured. The outside of the cylinder is supplied 



158 THE STORY OF A PIECE OF COAL. 

with an arrangement by which fine jets of water 
can be made to play upon it in the early stages 
of the reaction which follows, and at the end of 
from eight to ten hours the contents are allowed 
to run off into a storage reservoir. Here they 
arrange themselves into two layers, the top of 
which consists of the nitrobenzene which has 
been produced, together with some benzene which 
is still unacted upon. The mixture is then freed 
from the latter by treatment with a current of 
steam. Nitrobenzene presents itself as a yellow- 
ish oily liquid , with a pecular taste as of bit- 
ter almonds. It was formerly in great demand 
by perfumers, but its poisonous properties render 
it a dangerous substance to deal with. In prac- 
tice a given quantity of benzene will yield about 
150 per cent, of nitrobenzene. Stated chem- 
ically, the reaction is shown by the following 
equation : — 

C 6 H 6 + HNO3 = QH 5 N0 2 + H 2 
(Benzene) (Nitric acid) (Nitrobenzene) (Water). 

The water which is thus formed in the process, 
by the freeing of one of the atoms of hydrogen 
in the benzene, is absorbed by the sulphuric acid 
present, although the latter takes no actual part 
in the reaction. 

From the nitrobenzene thus obtained, the 
aniline which is now used so extensively is pre- 
pared. The component atoms of a molecule 
of aniline are shown in the formula C 6 H 5 NH 2 . 
It is also known as phenylamine or amido-ben- 
zole, or commercially as aniline oil. There are 
various methods of reducing nitrobenzene for 
aniline, the object being to replace the oxygen 



THE COAL-TAR COLOURS. 159 

of the former by an equivalent number of atoms 
of hydrogen. The process generally used is that 
known as Bechamp's, with slight modifications. 
Equal volumes of nitrobenzene and acetic acid, 
together with a quantity of iron-filings rather 
in excess of the weight of the nitrobenzene, are 
placed in a capacious retort. A brisk efferves- 
cence ensues, and to moderate the increase of 
temperature which is caused by the reaction, it is 
found necessary to cool the retort. Instead of 
acetic acid hydrochloric acid has been a good 
deal used, with, it is said, certain advantageous 
results. From 60 to 65 per cent, of aniline on 
the quantity of nitrobenzene used, is yielded by 
Bechamp's process. 

Stated in a few words, the above is the pro- 
cess adopted on all hands for the production of 
commercial aniline, or aniline oil. The details 
of the distillation and rectification of the oil are, 
however, as varied as they can well be, no two 
manufacturers adopting the same process. Many 
of the aniline dyes depend entirely for their 
superiority on the quality of the oil used, and for 
this reason it is subject to one or more processes 
of rectification. This is performed by distilling, 
the distillates of the various temperatures being 
separately collected. 

When pure, aniline is a colourless oily liquid, 
but on exposure rapidly turns brown. It has 
strong refracting powers and an agreeable aro- 
matic smell. It is very poisonous when taken in- 
ternally ; its sulphate is, however, sometimes used 
medicinally. It is by the action upon aniline of 
certain oxidising agents, that the various colour- 
ing matters so well known as aniline dyes are 
obtained. 



t6o the story of a piece of coal. 

Commercial aniline oil is not, as we have seen, 
the purest form of rectified aniline. The aniline 
oils of commerce are very variable in character, 
the principal constituents being pure aniline, para- 
and meta-toluidine, xylidines, and cumidines. 
They are best known to the colour manufacturer 
in four qualities — 

(a) Aniline oil for blue and black. 

Sb) Aniline oil for magenta. 
c) Aniline oil for safranine. 
(d) Liquid toluidine. 

From the first of these, which is almost pure 
aniline, aniline black is derived, and a number of 
organic compounds which are further used for 
the production of dyes. The hydrochloride of 
aniline is important and is known commercially 
as " aniline salt." 

The distillation and rectification of aniline oil 
is practised on a similar principle to the frac- 
tional distillation which we have noticed as being 
used for the distillation of the naphthas. First, 
light aniline oils pass over, followed by others, 
and finally by the heavy oils, or " aniline-tailings." 
It is a matter of great necessity to those engaged 
in colour manufacture to apply that quality of oil 
which is best for the production of the colour re- 
quired. This is not always an easy matter, and 
there is great divergence in opinion and prac- 
tice on these points. 

The so-called aniline colours are not all derived 
from aniline, such colouring matters being in some 
cases derived from other coal-tar products, such 
as benzene and toluene, phenol, naphthalene, and 
anthracene, and it is remarkable that although the 



THE COAL-TAR COLOURS. l6l 

earlier dyes were produced from the lighter and 
more easily distilled products of coal-tar, yet now- 
some of the heaviest and most stubborn of the 
distillates are brought under requisition for col- 
ouring matters, those which not many years ago 
were regarded as fit only to be used as lubricants 
or to be regarded as waste. 

It is scarcely necessary or advisable in a work 
of this kind to pursue the many chemical reac- 
tions, which, from the various acids and bases, 
result ultimately in the many shades and grada- 
tions of colour which are to be seen in dress and 
other fabrics. Many of them, beautiful in the 
extreme, are the outcome of much careful and 
well-planned study, and to print here the com- 
plicated chemical formulae which show the great 
changes taken place in compounds of complex 
molecules, or to mention even the names of these 
many-syllabled compounds, would be to destroy 
the purpose of this little book. The Rosanilines, 
the Indulines, and Safranines ; the Oxazines, the 
Thionines : the Phenol and Azo dyes are all sub- 
stances which are of greater interest to the chem- 
ical student and to the colour manufacturer than 
to the ordinary reader. Many of the names of 
the bases of various dyes are unknown outside 
the chemical dyeworks, although each and all 
have complicated reactions of their own. In the 
reds are rosanilines, toluidine, xylidine, &c. ; in the 
blues — phenyl-rosanilines, diphenylamine, tolui- 
dine, aldehyde, &c. ; violets — rosaniline, mauve, 
phenyl, ethyl, methyl, &c. ; greens — iodine, ani- 
line, leucaniline, chrysotoluidine, aldehyde, tolui- 
dine, methyl-aniline, &c. ; yellows and orange — ■ 
leucaniline, phenylamine, &c. ; browns — chryso- 
toluidine, &c. ; blacks — aniline, toluidine, &c. 

IX 



1 62 THE STORY OF A PIECE OF COAL. 

To take the rosanilines as an instance of the 
rest. 

Aniline red, magenta, azaleine, rubine, solfer- 
ino, fuchsine, chryaline, roseine, erythrobenzine, 
and others, are colouring matters in this group 
which are salts of rosaniline, and which are all 
recognised in commerce. 

The base rosaniline is known chemically by 
the formula C 20 H 19 N 3 , and is prepared by heating 
a mixture of magenta aniline, toluidine, and 
pseudotoluidine, with arsenic acid and other oxi- 
dising agents. It is important that water should 
be used in such quantities as to prevent the solu- 
tion of arsenic acid from depositing crystals on 
cooling. Unless carefully crystallised rosaniline 
will contain a slight proportion of the arseniate, 
and when articles of clothing are dyed with the 
salt, it is likely to produce an inflammatory con- 
dition of skin, when worn. Some years ago there 
was a great outcry against hose and other articles 
dyed with aniline dyes, owing to the bad effects 
which were produced, and this has no doubt 
proved very prejudicial to aniline dyes as a 
whole. 

Again, the base known as mauve, or mauveine, 
has a composition shown by the formula C 27 H 24 N 4 . 
It is produced from the sulphate of aniline by 
mixing it with a cold saturated solution of bi- 
chromate of potash, and allowing the mixture to 
stand for ten or twelve hours. A blue-black pre- 
cipitate is then formed, which, after undergoing 
a process of purification, is dissolved in alcohol 
and evaporated to dryness. A metallic-looking 
powder is then obtained, which constitutes this 
all-important base. Mauve forms with acids a 
series of well-defined salts and is capable of ex- 



THE COAL-TAR COLOURS. 1 63 

pelling ammonia from its combinations. Mauve was 
the first aniline dye which was produced on a large 
scale, this being accomplished by Perkin in 1856. 

The substance known as carbolic acid is so 
useful a product of a piece of coal that a descrip- 
tion of the method of its production must neces- 
sarily have a place here. It is one of the most 
powerful antiseptic agents with which we are 
acquainted, and has strong anaesthetic qualities. 
Some useful dyes are also obtained from it. It is 
obtained in quantities from coal-tar, that portion 
of the distillate known as the heavy oils being its 
immediate source. The tar oil is mixed with a 
solution of caustic soda, and the mixture is vio- 
lently agitated. This results in the caustic soda 
dissolving out the carbolic acid, whilst the undis- 
solved oils collect upon the surface, allowing the 
alkaline solution to be drawn from beneath. The 
soda in the solution is then neutralised by the 
addition of a suitable quantity of sulphuric acid, 
and the salt so formed sinks while the carbolic 
acid rises to the surface. 

Purification of the product is afterwards car- 
ried out by a process of fractional distillation. 
There are various other methods of preparing 
-arbolic acid. 

Carbolic acid is known chemically as C 6 H 5 (HO). 
When pure it appears as colourless needle-like 
crystals, and is exceedingly poisonous. It has 
been used with marked success in staying the 
course of disease, such as cholera and cattle 
plague. It is of a very volatile nature, and its 
efficacy lies in its power of destroying germs as 
they float in the atmosphere. Modern science tells 
us that all diseases have their origin in certain 
germs which are everywhere present and which 



164 THE STORY OF A PIECE OF COAL. 

seek only a suitable nidus in which to propogate 
and flourish. Unlike mere deodorisers which 
simply remove noxious gases or odours ; unlike 
disinfectants which prevent the spread of in- 
fection, carbolic acid strikes at the very root and 
origin of disease by oxidising and consuming the 
germs which breed it. So powerful is it that 
one part in five thousand parts of flour paste, 
blood, &c, will for months prevent fermentation 
and putrefaction, whilst a little of its vapour in 
tne atmosphere will preserve meat, as well as 
prevent it from becoming /fly-blown. Although 
it has, in certain impure states, a slightly dis- 
agreeable odour, this is never such as to be in 
any way harmful, whilst on the other hand it is 
said to act as a tonic to those connected with its 
preparation and use. 

The new artificial colouring matters which are 
continually being brought into the market, testify 
to the fact that, even with the many beautiful 
tints and hues which have been discovered, 
finality and perfection have not yet been reached. 
A good deal of popular prejudice has arisen 
against certain aniline dyes on account of their 
inferiority to many of the old dye-stuffs in respect 
to their fastness, but in recent years the manu- 
facture of many which were under this disadvan- 
tage of looseness of dye, has entirely ceased, 
whilst others have been introduced which are 
quite as fast, and sometimes even faster than the 
natural dyes. 

It is convenient to express the constituents of 
coal-tar, and the distillates of those constituents, 
in the form of a genealogical chart, and thus, by 
way of conclusion, summarise the results which 
we have noticed. 



-Is** 

_ o. a p 2 "C 






<3 



8. 
•3 2 

e 



+ 



R en 



S s 

O en 

U 
+ — 

13 



s.3 

a § 

° 6 

■8? 

"•S'3 

^O en 

o 
+ — 

(U 

S 

3 



♦J 
O 

o 



u 



.2 

a 

-I 

II 

-8 



s 



o s 

15 



*3 

_> o_ 

rt on 

cu O 

as 



.S 2 



OT3 



bJO 



rt 



— ~ 3- 

83 



52 



< 




INDEX. 



Accidents, causes of mining, 94. 

Age of Aa-og-ens, 23. 

AlethopteriSy 17. 

Alizarin, 137. 

American coal-fields, 146. 

Ammoniacal liquor, 137. 

Aniline, 136; dyes, 156-161 ; oil, 

159 ; salt, 160 ; tailings, 160. 
Anthracene, 128. 
Anthracite, 73, 74. 
Artificial turpentine oil, 127. 
Asphalt, 134. 
Australian coals, 151. 
A viculopecten^ 62. 

B. 

Bechamp's process, 159. 
Benzene, 126 ; dangers, 127. 
Bind, 42. 

Bitumen in Trinidad, 135. 
Blower, 88. 
Boghead coal, 129. 
Bog-oak, 69. 
Boring diamonds, 81. 
Bovey Tracey lignite, 72. 
British coal-fields, 140. 
British North- American coal-meas- 
ures, 149. 
Briquettes, 126. 



Calamites, extinct horsetails, 18. 
Carbolic acid, 163. 
Carboniferous formation, the, 37. 
Cardiocarpum, fossil fruit, 34. 
Carelessness of miners, 95. 
Causes of earth-movements, 56. 
Changes of level, 50. 
Charcoal as a disinfectant, 83. 
Chemistry of a gas-flame, 115. 



Chinese coals, 150. 
Clanny's safety-lamp, 90. 
Clayton's experiments with gas, 113. 
Clay, regularity in deposition of, 43. 
Club-mosses, great height of fossil, 

24. 
Coal, vegetable origin of, 11 ; formed 

by escape of gases, 12 ; not the 

result of drifted vegetation, 48 ; 

formed in large lakes or closed 

seas, 52. 
Coal-dust, danger from, 98. 
Coal formation, geological position 

of, 36. 
Coal-mine, the ; 84. 
Coal-period, climate of, 35. 
Coal-pipes, 94, 97. 
Coal-plants, classification of, 22. 
Coal-seam, each, a forest growth, 49. 
Coals of non -carboniferous age, 59. 
Coke, 139. 
Condensers, 118. 
Cones of Lepidodendra^ 26. 
Conifers in coal-measures, 32. 
Current-bedding in sandstone, 39. 

D. 

Davy famp, 90. 

Darwin on the Chonos Archipela- 

Diamonds, how made artificially, 78. 

Disintegration of vegetable sub- 
stances, 66. 

Disproportion in relative thickness 
of coal and coal-measures, 36. 



Early tise of coal, 101. 
Encrinital limestone, 46. 
Equiseta, 20. 
Essence de mirbane^ 127. 
European coal-fields, 141. 

166 



INDEX, 



167 



Evelyn on the use of coal, 106. 

Experiments illustrating fossilisa- 
tion, 18. 

Explosion, first record of, 89 ; ef- 
fects of an, 93. 



Firedamp, 88, 89. 

Fire in mines, 93. 

First light oils, 125. 

Flashing-point of oil, 131. 

Flooding of pits, 94. 

Fog and smoke, 107. 

Foraminifera, 45. 

Fossil ferns, 14. 

Fructification on fossil-ferns, 18. 

Furnace, ventilating, 87. 

G. 
Gas, coal, in;_ first use in London, 

113 ; constituents of, 124. 
Gasholder, the, 117. 
Glossopteris^ 17. 
Graphite, 75. 
Green Grease, 126. 

H. 

Hannay, of Glasgow, 79. 
Heavy oils, 126. 
Humboldt's safety-lamp, 90. 
Hydraulic Main, 117. 

I. 

Impurities in coal-gas, 123. 

Indian coals, 150. 

Insertion of rootlets of stigmaria, 

3 1 - . 
Insufficiency of modern forest 

growths, 10. 
Ireland denuded of coal-beds, 54. 
Iron, supplies of, 105. 

L. 

Lejbidodendra, 24. 
Lepidostrobi, : 5. 
Lignite, 71. 

M. 

Marco Polo, 134. 
Marsh gas ? 122. 
Medium oils, 126. 

Metamorphism of coal by igneous 
agency, 74. 



Mountain limestone, 44. 
Murdock's use of gas, 113. 
Mussel beds, 63. 

N. 

Naphthalin, 128. 
Neurofiteris, 15. 
Newcastle, charters to, 103. 
Nitro-benzole, 157. 

O. 

Objections to use of coal, 103. 
Oils from coal and lignite, 12. 
Oil-wells of America, 131. 
Olefiant gas, 123. 
Orthoceras, 62. 



Paraffins, 122. 

Peat, 68. 

PecofiteriS) 17. 

Pennsylvanian anthracite, 147. 

Persian fire-worshipers, 133. 

Pitch, 126. 

Plumbago, 75. 

Polyzoa, 62. 

Prejudice against aniline dyes, 162. 

Prohibitions of the use of coal, 103. 

Proportions of explosive mixtures, 

„ 9I * • 
Psaronius, 17. 

Purifiers, 120. 

Pyrites in coal, 139. 

Q. 

Quantity of coal raised in Great 
Britain, 154. 



Reptiles of the coal-era, 60. 
Resemblance of American and Brit- 
ish coal-^?(?r«, 54. 
Retorts, 117. 
Roman use of coal, 102. 
Rosanilines, 162. 
Royal Commission of 1866, 153. 

S. 

Sandstone, how formed, 38. 

Shales, 42. 

Sigillaria, 28. 

South American coals, 149. 



i68 



INDEX. 



-Spores of lefiidodendron, 26 ; resin- 
ous matter in, 28 ; inflamma- 
bility of, 100. 

Steel-mill, 90. 

Sternbergia^ 33. 

Stigmaria, 30. 

Subsidence throughout coal-era, 55. 

Sulphur in coal, 106, 139. 

Sussex iron-works, 105. 



Tar, 125. 

Testing pits by the candle, 89. 

Texas coal, 148. 

Toluene, discovery of, 157. 

Torbanehill mineral, 130. 

Trappers, 88. 

U. 

Underclays, 30, 44. 

Uses to which coal is put, no. 




Vaseline, 131. /*- *-*^ 

Vegetation of the coal age, 9. ^j -J 
Ventilation of coal-pits, 86. 



W. 

Washers, 119. 
Waste of fuel, 109. 
Weaiden lignite, 72. 
Westphalian coal-field, 10. 



Young's Paraffin Oil, 129. 



Z. 

Zoroastrians, 133. 



(8) 



THE END. 



IHHllil 



Wm 







